I'm running a 68 400 in my 65 goat that has been built at .40 over with 75 6X heads (94cc), block decked, heads milled and a ram air IV cam with rhoades lifters. C.R. is stated to be 9.25:1 and low end performance is pathetic. This is a four spd car with a 3:23 axle. I want to switch to a Lunati Voodoo cam and Lunati recommends their p/n 10510702 262/268 which is a hydraulic flat tappet cam. If I use this cam can I retain the heavy valve springs currently installed with the ram air IV cam and should I change the push rods? This setup has only a few hours of run time since the complete rebuild. I'm also using an 800 cfm Rochester quadrajet stage two which loads up at low end. Is this due to the cam? In fairness the car will perform well when you hit the 5000 range but this is not a good setup for a daily driver.