I just got my 454 machined . Nothing radical; pistons .030 over, crank .010 under, new rings, bearings, etc. I was running a 750 Holley vac. secondarys. So i decided to go bigger with the fuel system and bought a tunnel ram with a set up for two carbs. My dilemma is the carbs. I was thinking two 650 Holleys., but I don't know if you should run vacuum secondaries or mechanical secondaries or if even matters. I haven't chosen a cam yet because I wanted to get the tunnel ram first. Any help from you guys would be very much appreciated.