Re: ZR2 rear axle questions
I've got a ZR2 and one thing that I can tell you is that the 31" AT's that come on it stock barely fit (mind you a stock ZR2 already have a 3" suspension lift AND trimmed front fenders). I presently run 32x11.50 MT's on my truck and cornering over a bump causes them to rub from time to time on the back of the fender SO I don't think 31's will work that great on a 2WD that likely sits lower in the front than a stock 4WD in the same model, neither of which have the trimmed fenders. Even if you do some front end suspension work on the truck, you still may need to trim sheet metal.
ZR2 axles are ALL 3.73 ratio, to the best of my knowledge. I have NEVER heard of a ZR2 with 3.42's or 4.11's unless it was a custom, aftermarket setup.
The ZR2 rear would probably be a nice addition to your truck, though. Everybody says that 10 bolts are 'weak' - well, the only one I ever 'broke' was used, abused, and had 240k miles on it. The failure was carrier related (retainer screw fell out) and could have been prevented if I would have paid closer attention when changing the fluid one time. A new carrier (not really necessary, just wanted a better posi unit), the same gears, and I still use the axle today in my plow truck.
<font color=blue>Two wrongs don't make a right, but three rights do make a left.</font color=blue>