The higher effort 6bbl FAST motors were around 625hp with ex manifolds and 2.5” exhaust pipe....... ported 906 heads.
No vacuum pump, stock Hemi style oil pan, non-oxygenated fuel.

Take one of those builds, use a race oriented single plane intake, add headers, and a cam to take advantage of the better intake and exhaust....... should be worth at least 50hp...... so that would put you at 675hp....... with better heads you should be able to find another 25hp...... which would put it around 700hp.
Good pan, vac pump, q16....... should add even more.