Why cast? Build a styrene box to the same dimensions, and raid your spare parts boxes for a couple of hubcaps, a six volt battery or whatever you want on it. You said you were going to modify it, correct? No need to make it any more difficult than necessary. It is a pretty cool piece.
Remember? I've got one. CBs are still heavily used by motorcyclists. A CB was a factory option on my 2007 Honda Goldwing (and has been every year since 1980 or so). I use it to talk to my buddy with the standard factory CB on his 2014 Harley Davidson Ultra Classic. They are both fully integrated into the bikes - you'd never know they were there.
Revell did a 1/25 2000 Ford Limited Edition Harley Davidson F-150 that included a trailer and Harley motorcycle; it might be an FX something or the other. It's not a Softtail. This would be the second kit I've heard of by a company named Sunny; the first is a Cobra 427. I don't know much about them either. According to a website I found, the first letter will always be F (Big Twin), X (Sportster) or V (Revolution/Vrod). No mention of S, but F can sound like S sometimes.
Here's a website for you to check out: http://dieseldetailer.proboards.com/ . Lots of information on detailing diesel locomotives and parts. I would imagine that someone on there would have the parts you are looking for.
For those of you near Baltimore, it is supposed to be there soon. Zumwalt has left Newport, RI to come to Baltimore where it will be commissioned on Oct 15. I haven't been able to find an arrival date in Baltimore yet. I'm hoping they'll give tours.
Mine had the same mold lines on the pillars - a few seconds with some 320 grit sandpaper got rid of them. I was planning on BMF for the headlights, but I'm not sure how that is going to work out yet. I think you'll be able to see the body color through the clear parts of the taillights, so probably the same for them.
I picked one up yesterday, too. The body, unlike the AMT 2010 and other Camaros, has the hood and front and rear fascias molded to the body. The window surrounds are pre-painted, and it has separate windshield wipers. Two identical appearing decals and sticker sheets are included, which have a pair of black stripes for hood and trunk along with the various gauges and emblems. The brake rotors include caliper detail, and they are mounted so that they don't rotate. The wheels are mounted using the trusty steel axles. It has a nice platform interior. The kit is molded in 3 colors - red, black, and gray, plus my favorite color, clear. The taillights are molded in clear, and pre-painted red in what I assume are the appropriate places. Only the wheels, interior rear view mirror and I assume it's the rear license plate are chrome. Looks like I'll have to break out the BMF for the outside rear view mirrors. It seems to be a pretty nice kit. I haven't found anything to complain about so far, even though I wish the hood and fascias were separate. Looking forward to building this one.
Unfortunately, Revell paints are not sold in the US so I can't make a comparison. I have found the Tamiya paints don't work as well for brushing as, say, Testors. Tamiya metallic colors do seem to work pretty well for me. I've been using other than Tamiya for most brush painting.