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How to replace a roof on a car? 4 door to 2 door 59 Desoto?

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Hi everyone, Im wanting to build a 1959 Desoto 2 Door Hardtop. I have a X-EL/Johan 1959 Desoto 4 door as my starting point & a AMT 1957 Chrysler 300 2 door hardtop kit. I'm thinking of cutting the roof off the 4 door Desoto & grafting in the roof off the 57 Chrysler.
Question, Where should I make the cuts? Obviously cutting the roof off each at the bottom of where the roof pillars come off the body you will loose some material off the roof. Will it start to look like it has a slight chopped top? Any help on where to cut would be great.
Second question, Ill need to rescribe the doors from 4 to 2 door & fill in the old door lines. Can this be done without ruining the side trim? Or is it easier to sand off all the trim & re-make it from thin styrene?
Any help would be great. Ive built a lot in the past but never cutup bodies to much. Ive also modified side trims but I usually sand off & start from scratch. Thanks for your help!



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I've done a couple roof swaps and I can tell you that not all applications will apply. Each model will have (or need) its own way of doing a swap. It can depend on the manufacturer and how "true" to scale said car is. On that note, I'd strongly advise measuring out your roofs as best you can to see how much of a difference there is, if there's any at all.

If these were two Johans, I'd say you may not need to worry about that at all. But, being that the '57 is an AMT kit, I'd not be surprised if it's a bit on the large/wide side for 1/25th scale. Johan was notorious for "undersizing" their models to suit whatever box they needed to go into. This was a store request kind of thing due to the fact that whatever outlet Johan wanted to sell their models in, the stores needed to have the model boxes fit in whatever space was available. In the '50's and '60's this was a widespread practice particularly with Johan kits.

As far as your '59, I'd not cut the roof below the A pillars. Reason being is that the windshield frame A pillars are a bit different between 1957 and '59. I'd cut it along the windshield header and then graft the '57 roof on to that.

On the rear part of the roof, I'd try to cut just outside of the C pillars and leave a bit of the tulip panel (the area between the rear glass and the trunk), so you'll have some play around room to sand/file for whatever is needed.

If you take a look here, you'll see pics of a '59/'60 Chevy Impala roof swap I did years ago. I was able to do pretty much a direct transfer of the roofs as they're from the same maker and scale. In fact, the '60 (which had a MUCH better roofline IMO) was derived from the '59 as far as tooling.

As far as your door lines, if I were building this, I'd try to keep as much of the original trim as possible. I'd start the scribing of the new lines on the trim, and work outwards from there. You might want to look into something called "Dymol Embossing Tape". This is the tape they use to stick on items in the store for pricing and such. Very nice and rigid, and just the thing to use when you want something sturdy to re-scribe new lines into plastic.

One more word of caution............I don't know how old that X-EL Promo is, but be careful because as kit plastic ages, it can tend to get BRITTLE. I'd work carefully and slowly cutting the roof as you don't want any surprises.

Hope this helps!

Edited by MrObsessive
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One other thought..........knowing how "obsessive" I am about rooflines and such, I'd want to keep the '59 roof as a parts donor as that can be used for another swap later. In fact, as I was typing my last post, a '58 Plymouth four door hardtop came to mind. Or perhaps, a '57 Desoto FireFlite four door hardtop? The rear part of the roof would need some subtle reshaping for '57-'58 (lower), but a number of cars could be done from that.

One nice thing about those old Johan bodies is that they were pretty much right on the mark when it came to accuracy. In fact, I believe Johan is the only manufacturer to ever do that 1957-'59 Mopar four door hardtop roof style. 🤔

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I've done a few roof swaps and one thing I learned is that you want to use as much of the donor roof as possible. If the cowls are the same, swap those also. Try to keep the donor roof as a unit. That way, your windshield and backlight will fit like they should. Also, don't cut horizontally. Cut vertically. You won't lose any roof height. 

I usually cut just behind the vent window. Then, either cut some of the door with the vent window or right against it. I'll cut the cowl right on the panel line. At the rear, cut in front of the C pillar, take a little of the quarter and cut a straight line across the tulip panel or cut right with the panel line of the trunk if they're the same. You can add a strip of styrene underneath for strength.

The most important thing to work like this is taking your time to plan and execute the cuts.

This model is nothing like yours. But, it demonstrates my method pretty well.


The roof actually slid down inside the body. 

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Thankyou for everyone’s reply’s & your amazing help. I must admit I’m not overly confident but I’ll give it a go.

Yes MrObsessive I was thinking the AMT may be larger than the johan. I will measure it up. I do have some other Mopar Modelhaus kits but that is an absolute sin to cut up a Modelhaus for its roof. I also have the Johan 60 Desoto kit but would prefer to not cut the roof off that either. I guess what I’m saying is the AMT Chrysler kits would be the cheapest alternative. 

Wow Steven, Your 59 Convertible looks amazing. Is that bare plastic or has it been under coated? Can’t even see where the rear door was. I can only hope mine turns out as good as that. 

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2 hours ago, mopargreg said:


Wow Steven, Your 59 Convertible looks amazing. Is that bare plastic or has it been under coated? Can’t even see where the rear door was. I can only hope mine turns out as good as that.

It just has one light coat of white primer as a guide coat.

Still has a lot of work to be done, but I got a start on it anyway. ^_^






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When i was a little squirt of 6 or 7 years i used to walk by a 1959 DeSoto that was parked 2 doors north of our house. I was on my way to a big pond where i would blow up frogs and birds with my BB rifle. The DeSoto was owned by an elderly woman that we rarely saw and all i ever saw was the rear end of that car. But at that age i was seriously impressed by those jet-age fins and red tail lamp exhausts.

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