Bracket engine, what would you build and why?

Have I been there done that...NO!

But if you're not set on going faster and truly want to win races with consistency, I'd do the 440, since you already have the headers for the tall deck. Lets face it, 500hp in that light car would easily run somewhere in the 10's and still keep you in your track programs "fast" bracket.

I'd look into a moderate compression forged rotating assembly, and I'm sure someone here could guide you toward one that's solid for many runs...like hundreds if it's cammed and sprung properly :D.

In my opinion, screw the "big" numbers. Just build a solid engine that just needs a oil change or two, and a valve clearance check every now & then.