[bobcowan]

The first 400hp are pretty easy. Just about anybody can do that in their garage. It's the following smaller increments that are more difficult and more expensive.

Once you put the parts together, you have to spend time and money getting them all balanced and tuned properly. Don't be afraid to spend money at the dyno for a real tune, not just a power run.

I think you have too much timing; but it could just be semantics.

If your base timing is around 10-12*, and you add 32* of advance, you have 42-44* of total timing. Waaaay to much. And that is probably why it ran better on race fuel. Most SBF's tend to best around 34-36* total. Set base at 10, and 24* in the distributer and see what happens. You can experiment by moving the base up to 14* - for a total of 38*.

Carb is maybe too big, but maybe not. I'v seen lightly modded 351W's do very well with a 750 carb. Your dyno time will tell you what to do there.

The cheapest and easiest power usually comes from compression. Change the pistons and get compression up to around 10.5'ish. That much compression at low altitude needs carefull tuning, and conservative timing; especially with cast iron heads. But it does make good power.

You can shave the heads for more compression. But that changes valve train geometry, valve to piston clearance, and changes the swirl pattern.

Changing the exhaust might be difficult to do. Depends on what you have, though.

Take a close look at your air cleaner. The thin Cobra oval air cleaners really cost you power. Use a round one, as tall as possible. And use a K&N filter top. That's usualy worth a few ponies right there.