niko, i will give you some things that are EXTREMELY important. the numbers i'm giving you are 1:1 numbers. this is so anyone can use these numbers in any scale IF THEY WISH TO.
we've all seen cars that are narrowed way too much. so much that the rear w/ wheels and tires on it won't fit inside the quarter panels. ovbiously "too" narrow. the rear width of the body can be determined by the width of the 4 link system you choose and the width of the tires plus clearance. on most pro mods and please note i said MOST pro mods ( i'm sure there are some out there that may be different) the four link system is between 16 and 20 inches on center (you can go to wark williams or strange engineering websites for their availlable widths). to get to the outside dimension of the 4 link add 1.5" you'll need 2" clearance on each inside of the tire. the cross section of each tire is around 22" ( you can go to goodyear or hoosier or m/t website for their info.). then add 2" per side for body clearance. so here's the tally.
16.0" center 4 link
1.5" to get to the outside dimension of the four link
4.0" inside to frame rail clearance ( l&r sides added together/ 2.0"per side)
44.0" cross section width of both rear tires (22" per tire)
4.0"body clearance (l&r sides added together / 2.0" per side)
69.5 total body width needed for this combo.
you can see the pro mod camaro body dale posted has a 70.125" width between the rear quarters over the tires.
if you want to build your body using 1:1 info. as a base for the body. i can go on.
I FIND the biggest mistake a builder can make, when starting a build like this, is not getting all of your thoughts together, not getting accurrate info. and not developing a plan on how to execute the build.
jumping in with both feet and no game plan is a sure recipe to building a "junker" as dale calls them.