Most of the T-Q's are 1 3/8" primary 750 cfm , some of the '74 and laters with 1 1/2" primary and were 850 cfm. If I remember right the early '71's were 800 cfm's. All have 2 1/4" secondary. As far as performance, the '71's made more power on the dyno for us with the 340 & 360 engines...
All around 750 cfm carb's is your best bet with something with a little power...