Welcome to CHR, Len! A '57 Ranchero will be a super cool project!! Like Dave, I've not been a fan of the old on new approach. The modern frames have so many bulges, bumps and brackets that they just don't seem to fit just right, or if you can get them to fit then they tend to look "different". The '57 Ranchero can be a car/truck of considerable value if updated like Dave mentions, but dropped on a later chassis is not really a '57 any longer in many peoples eyes. Like a guy I met that had a cherry 1940 Ford Pickup, and he set it on a Chevy S10 chassis . He loved his truck, but it wasn't a '40 any longer - it was a S10 with a sweet 1940 body, and he got judged accordingly at cruises and shows.

BUT, it is indeed your project, and there have been a lot of these grafted projects done and they look great from the top side. If it's what you want to do then get the front track to match your needs, and go from there. I'm surprised that the Crown Vic chassis isn't waaay too big, but if you've got a salvage yard you probably have that scoped out already. Either way you go, I hope you'll stick around and let us watch your project as it evolves. It's all about doing things the way that YOU want them, not pleasing everyone else, right?