I feel aunty is something that is best forced induced. Gives a much nicer power delivery that way. Especially if you have a cam profile with a longer duration and lift, as it will keep you on your powerband for longer.

Alternatively you can try a different bottom end, with a wider bore and longer stroke but you'd best raise your compression ratio. Go a thinner gasket if you have to, and use thinner weighted oil.

I'll see what i can muster fella. How many cylinders would you prefer?