choosing a converter and gears

ok so i need help choosing a converter and a gear ratio meaing what gears to buy these are my plans

carb:650-700cfm
intake: rpm air gap
cam: still not sure but maybe dur:270/270 lift lift:420/420
headers: hooker comp or super comp maybe tti
exhaust: 2.50 with 2 chambers X pipe
pistons:9.24.1
heads: 88 302 heads with 360 valves



for the converter i was thinking maybe like 2800-3200 and for the gears maybe 3.55 or 3.90

but any help is better then me guessing thanks