650 dp vs 750 dp in a 408

I've been trying to decide on a Eddy 650 or 750 for my 68 340 Eng.20 over, 10:5 Comp,Eddy heads, air gap intake, Stock exh.manifolds with 2.5 Exhaust ,4 spd. , 323 gear. I thought 750 would be too much but others say it would be fine. Car is a driver. Being a driver I'm still leaning toward 650.
In your case have you run them both in the 1/4 mi. ?