10;5 if it is mostly street. 13 and over if it is mostly for racing. Forget the power difference. DEcide what you want to use it for.
the 502 production block is factory rated for 750 hp max. I know of a few guys doing over 800 with them. It is the weakest factroy GM BB Block ever built. Will still make a great street engine though.
I prefer the ARP 2000 bolt upgrqade to the L-19. Go to ARP site and check out the different alloys and positives and negatives of each and make up your own mind.
Shafiriff does a good balance job.
I suggest to inquire about their pump gas cams for your type of engine if you do this for street.
Ed