Yeah, they are perimeter frames so it's tricky. Like has been said, if it ain't broke don't fix it but seeing that your overseas, I'm guessing there's a factor of availability that plays into it to for you.
Tex Smith
(Amazon Link) Covered using a perimeter frame in one of his books I'm thinking it was
How to build custom cars... In that book he took a perimeter frame car, cut the center (Wide) section out and replaced it with rectangular tubing which allowed him to get whatever wheelbase he wanted. I think it was under a Merc. Also Ed at E-Z Chassis Swaps was working on a kit for those trucks on the caprice style chassis and it put the rails out into the step area in the cab, it didn't look to bad with it boxed off but not sure how I felt about it. Also the rear frame kick up necessitated raising the bed floor up too, which I'm not a fan of.
It comes down to 3 factors in my mind whenever this comes up; What you want the finished truck to be like, What your skill level is, and Money. If you have cheap donor parts available or more available than stock or "kit" parts, and you have the time and skills then it might be worthwhile to try.
Mongo
