350c or 200

[turbo buicks]

i got a 200 with good internals but needs 1-2 band. i got a guy whose a great builder or transmissions and he says for 400 he ca either fix my 200 or build a 700 hp capable 350C. what do i do? i want a reliable trans but at the same time i wont be driving as much as i used to at all. car wil have 72 turbo, heads, cam etc looking for around 600 or so rwhp.