Go V8 then, you could dump $3,000 into that slant and still barely make 300 HP unless you added forced induction. Sounds like you know your way around modifying old engines, some guys come on here with zero experience asking the same kind of question about a SBM build/swap so we tend to be "conservative" in our recommendations off the bat.
That 3.23 gear would work well with a mild 318 and the deep 1st gear of your A-833 OD, and you would be able to actually use 4th lol.