in the last image from geronimo, that truck sitting on the frame with the rear end sitting low, the way the front wheels sit in the fenders would say to me the tires are not gonna turn without hitting the fenders.
I have my truck sitting on an envoy frame. the envoy is wider. I locked the suspension at the normal ride height, front and rear, before taking the body off. that way the truck, when done, will (be made to) sit with the suspension sitting the way it was made to sit. when done I will adjust the springs out front and rear if the ride needs to be changed in order to achieve the correct height (coil over strut style is stock up front with an upper and lower control arm so lowering shocks and spring kits are available because there is a performance model in the gm lineup of this unit and out rear an air bag suspension was available as a stock option so I can remove the stock coils and install the stock airbags out back in about an hour minus the air lines etc). I say this because the frame swap needs to have the suspension sitting like a stock truck so it works properly and steers properly. take a heavy truck, remove the body and install a light truck on top and the suspension is bound to sit higher than it used to. that means the suspension doesn't work like it should. the lower control arms are made to sit level with the ground when viewed from the front. the upper control arms work in conjunction with the lowers to make the tires angle in or out at the top depending on where in the suspension stroke they are and whether or not the upper and lower arms are the same length.this is done by the different arcs that the arms go through. this is important for a frame swap because if the suspension is allowed to sit with the lower control arms at a downward angle, like there is less weight on them than normal, then as weight comes onto them as you go over a bump and the suspension moves upward the tire will move further towards the fender at the bottom because the ball joint end of the control arm will move outwards as the arm moves upwards. the upper control arm may also skew the tire angles further depending on the set up. it's important if the tires are already close to the fenders like the pic mentioned if this is confusing you could google it for some steering geometry diagrams but suffice to say you probably should put the suspension through a complete cycle from lowest to tallest with the tire turned hard both ways in order to see if the tire rubs or comes close enough to rubbing so after an alignment, when stuff can change a little due to shimming etc, you don't end up with a surprise. shorter control arms compound the difference because they have a smaller arc of movement so a small upward movement canmean a bigger difference in camber
on my frame swap the wheels are already fairly flat faced as stock wheels. I have installed a shorter tire than stock because I like that look on these trucks but still will do the full suspension travel test with a full tread tire. i plan to grab a set of nicer wheels with stock offsets when done but will mock up with these stock wheels. if there are issues during mock up I plan to flare the fenders to accommodate or space the truck off the frame a bit until tire interference is not an issue.I have included a pic of my set up looking through the headlight hole at the tire so you can see the tire to fender clearance. changing the tire size also affects the steering scrub radius angle the same as changing a bunch of wheel offsets would do so it becomes important to keep track of all the changes done in order to have a truck that is fun and safe to drive.
here is a little wheel calculator that has a diagram of the suspension changes
https://www.wheel-size.com/calc/?whe...cl=50mm&sr=0mm