Frames have been 34" for many years, probably since the mid 50's or 60's. However, frame width depends on the length of the cross member. The first frame stretch I can remember doing was on a 1956 GMC 550. I added a drag axle and used piece of frame from an R190 International. We now use what is referred to as tanker spec cross members to accommodate a glove because a cross member has to be shortened 3/4" to accommodate a 3/8 glove. 5 piece are a c channel with 2 gussets at each end. 7 piece have another gusset over the top.