Thinking of changing direction with my engine. Opinions needed

The question is will it run well with the aluminum heads - yes, it will work fine. Probably make a little more power than you currently do. Will it pass 400hp? Who knows. What does it make now (measured, not a desktop hp number)? With that cam, RPM heads, built well with good ring seal and good machining - it should be close to 400hp. No clue if yours does now tho.
In terms of the six pack - tuning is the same as a 4bbl but the intake is restrictive so you could make more power with a quality dual plane. There are guys on here that can help with tuning any engine combo. It starts with timing, and ends with carburetor.