Yeah, I go for the frame shortening also. You have to cut it in the middle where it is same full depth, don't try to move the axle up the frame. the frames get smaller where axles bolt on. A GMC manual usually has sections on frame repairs and shortening, that the Chevy ones don't. Check one out. Is this a one wheel rear with a long step bed, or a flatbed? Probly easier to shorten a flatbed than step side. Look at other option, a BIgger garage! Now's your chance to build a nice shop, make it long and tall for the bigger trucks. OR, add on to end of your existing garage?
