You're building box-stock? Well, at least we know it's gonna be the cleanest box-stock build ever, that's for sure. I've never seen one of these outside of pictures, I always thought it was a gorgeous car.
Marcelo. and even easier method of making the wheel well trim is the angle styrene strips that Evergreen makes, I've used it many times. You simply lay it in the wheel well, glue it down, and foil it! Here's the angle strip in place and foiled on a '68 Satellite I did a while back, since I still can't get a picture to load, you'll have to click on the link.
BTW, my name is Mike, the Olaf is just to mess with people! http://media.fotki.com/1_p,sgqqwgrtkrbtbrgxtbbfqgtgtsbk,vi/kkdbqktbxttsrkfrwk/1/879761/9764454/Jays68Satellite0131-vi.jpg
This looks like it going to be a beauty when you finish it, and it seems like your skills have increased just a bit since the last time you tackled this model! Great work on the headlights so far and fenders, it really does make a difference! Lowering the nose a bit is also a good idea, I always thought this kit sat a bit too high, at least for my tastes!
I prefer the "Eyeball it, cut, cuss a lot, measure, cut it wrong again" method, it's so much more satisfying when you finally get it right! Ben, who care how long it takes, build for yourself above all, and every mistake you make will just make you a better builder in the long run. No matter what, finish it off, even if it isn't what you pictured in the first place. The biggest stumbling block to scratch-building and customizing is not finishing. Once you've got some success under your belt, whether it's right or not, you can move on to the next one with the confidence that you'll finish. And amazingly, the next one will be better!