[truckster]

I've seen them turned as far as 30 thousandths. That probably wouldn't keep me from building a motor I wanted to build, but... it kind of sounds like you're looking for a reason to go newer. I just built an L31 Vortec for my Blazer and I'm really happy with it. You get a 1-piece rear main seal, roller cam, and Vortec heads (plus about 100 horses) in the deal. If you go that way, you'll need to change the flexplate or flywheel, get a new intake (different bolt pattern) and depending on the block, you might need an electric fuel pump.