Here's my update.
The 2wd crossmember won't physically fit on the blazer frame. The frame appears to be too wide. I'm working on squeezing it down with ratchet straps, but so far it's not enough. I may just have to cut the stock blazer frame bracing off then try again...DANGIT!...I hate cutting these huge factory rivets.
EDIT:
Looks like the previous owner slammed the truck on a rock/boulder or bottomed it out hard and bent the frame up pretty good, that's why the crossmember woundn't fit. The section where the crossmember goes was hit from the bottom and dented in and that pushed the side out. It's ugly and really disappointing. The frame is also cracked in two spots where the steering box goes. Any suggestions? Should I stop while I'm ahead?