I ran a 6V=71 on a stock 340 block for over 20 years at 13lbs. Even detonated 2 sets of pistons learning to tune. Never hurt the block. We also run a stock 360 block/cast crank at 21lbs. A buddy has run a stock 440 block, iron heads, 8-71 on alcohol to 5.60's in the 1/8. A sensible tune , thick crown pistons it'll be fine for mostly street.
Doug