750 hp is possible with a low deck stroker using TF 270 heads and pump gas compression but it will be an expensive engine to build. If it is for a race car you can add some compression and that will add power. Race headers and open exhaust will also help make power. 800 hp can be done by using an Indy head, maybe a CNC ported -1 head. I'm not so sure shooting for 800 hp is a good idea with a stock block though. You'll eventually bust the block and it could get ugly when the block goes. Cracking a block in the lights could result in a total loss of the car.

Grays Automotive in the Portland area has built a bunch of 700+ hp low deck stroker engines. I just helped them dyno a 700+ low deck 512 last week and they built both of my 470 engines. My dry sump 470 made 780 hp with TF 270 heads and pump gas compression but it had a lot of high dollar parts in it. Probably cost over $20,000 to duplicate that engine.