'74 is a good block. I would use ARP head and main studs good gaskets. -Think about a half fill with hard block. Main girdle couldn't hurt.
Build the hell out of your cooling system.
If built right, a stock 351w will surprise folks with its strength. Im going to be pushing 600 fwhp on my stock crank '78 block. I have good rods, good studs, good cooling/oiling system. I built it myself, and I know it was built pretty good. Block strength isnt worrying me at all.
Look at toohighpsi.com That guy takes stock truck 351's, throws rings and bearings in them, reusing the stock rods and CAST pistons-then runs 10's with them. He hasnt melted a piston, (he has blown a stock rod or two). Stock crank and block live.....