Before switching to the R302 block I have now, I had a stock block that I used for 3 years at about the 600 + HP level. I used an old spec racers trick and had the block cryogenecally(sp) frozen. Even having one N2O mishap, and losing a piston, there was not a mark on the block and I reused it again. That plus a main girdle, and ARP hardware kept me racing for 3 years seeing the track almost every weekend. Cost is about $1.25 per pound. For more information on this process go here:
http://www.onecryo.com/motorsp.htm and look at some of the pro's in the NHRA that are using it.
Ron