How many HP do you want?

I have a 390 in a 67 FB Mustang. It has the Edelbrock Performer RPM top end & a crane cam of unknown grind. It makes around 425 HP & revs to about 6500 rpm. I didn't build this motor, it came with the car, which is probably why it has dropped #6 cylinder.
If I was rebuilding it I would stroke it to 410 cid & fit a different cam to keep the revs at around 6000 (revs is what kills engines)I would think you could get 450 hp out of a 410 stroker with no great difficulty and very good reliability, if you want more hp than that it can be done but you will start to trade off reliability

regards

David