so after a couple hours of measuring and remeasuring I decided I had the crossmember in there pretty dang square. about a 16th. The frame itself was the squarest GM frame I've ever seen 1/32 in the front end. I think they really improved their build quality over the 60-66 trucks I am used to messing with. I've seen clean low mile 60's trucks off a half inch. You can see my little tabs tacked on in this pic. Also drilled the frame for the crossmember bolts and tacked the nuts for ease of removal