Well, here is my look on the subject. There is no way to standardize what hits and what doesn't. There are too many dependent factors like:
- Type of lift
- Manufacture of lift
- Spring condition
- leaf count
- leaf thickness
- actual tire size
- actual tire width
- advertised tire size
- advertised tire width
- wheel size
- wheel width
- wheel offset
- driving habits.
All of those make up what will hit and what won't.
For some examples -
long ago the camo RC had a 4" rough country lift with 3" body lift and 33x12.5 BFG all terrains on 15x10 aluminum wheels (not sure of offset, tire stuck out maybe an inch, probably less, outside of fenders). I hit the fenders while offroading alot, even in the rear. I run my trucks very hard.
The new RC we have came with stock height, same tires on 15x8" aluminum wheels and I never hit the fenders. I never ran it hard in stock form (different story now

)
Now, the 4" rough country lift was pretty flexy and the new RC had some very good condition springs for an 84 (still had arch front and rear). Theoretically same size tire, 7" of lift hit, but stock didn't.
This is what I want to stay away from - We list 33's will fit with a 4" lift (which is usually correct). Then Joe Schmoe comes to the site looking at running 33's on his fully restored 74 RC. He buys 33" swampers (true 33" diameter) x 14" wide tires and mounts them on 12" wide wheels.
The first time he goes off the highway (driving to his deer blind maybe) he tears the hell out of the fenders and brand new tires, gashing the sidewall. He comes back and tells us our shit ain't right since he ruined his new body work and paint and practically destroyed his new tires.
My point is there is no way to accurately say what will hit and what won't. And if we standardize it, and some new people come along and go with what we say and their stuff gets screwed up they will blame the site, since the site said it would work.