91 s10 measurement ?

i took a couple measurements of the rear end centered in the bed, then pulled my rear end out to weld my tabs on. now the trickey part i lost my measurements. where are good spots to measure of to get it centered foward and back and side to side. also how far back should the rear end be say from the back cab wall. its a 91 s10 extended cab

thax

did you just weld tabs on the rear end and not install any 4 link or anything?

yea no tabs were welded on