Actually, I believe it probably had a semi-floating 14 bolt. It has a 9.5" ring gear, and a more rounded housing. I priced ring and pinions for this particular rear end and found they were kinda spendy. Somewhere around $250 just for the parts (install kit included) which is more than you'd pay for something like, say a dana 60. Anyway, I wouldn't try the junk yard approach, and have a shop install the gears for you. There are a few things you have to get just right, like gear lash, and it's worth the money for the peace of mind. 3.73 will also work just fine I'd imagine. Won't suck so much gas either. You might want to find out for sure what your gear ratio is before you swap, because perhaps if you have 4.10 gears now, and want to drop your RPM a lot, 3.73 might not be a big enough change. Going taller than that would seriously cut into towing, hauling power. 3.42 is the next taller ratio I have seen for sale for that rear end. Sorry about the essay I just wrote, but to sum it up, find out what gear ratio you have (count teeth on ring, devide by teeth on pinion), find out what rear end you have (14 bolts on the cover, and semifloating would be the GM 14 bolt 9.5" ring gear, semifloating means that there's no big hub sticking out of the wheel on the end to make it simple) and have a shop put in the new gears when you get them. Good luck.