Duke, some of the best-running 350's I've built ran a Comp Cams hydraulic setup with about 290 degrees of duration, and around .425" to .450" lift, at 106 degree lobe centers. Unless you're going to run above 6,000 RPM regularly, the 1.94" intake valves are all that's needed. Increase the size of the exhausts to 1.6", and do a good pocket porting job. If you're not worried about passing an external inspection, round out the exhaust ports to match the diameter of the headers. Use equal-length header tubes for all cylinders. If the port modifications can be inspected by just removing headers/manifolds, keep them stock-appearing. With the above setup, plus flattop forged pistons and an Edelbrock 650 CFM carb and matching intake, you should see 500+ HP and still have pretty good low-end torque. Use an ignition system capable of 6,000+ RPM without spark scatter, something like a Mallory Unilite or an MSD.
The 305's were all-out race engines, with 3" stroke lightweight cranks, for a CID of 255 cubic inches. The rotating assembly, consisting of a 38-lb. billet crankshaft, Honda-sized H-beam rods, and ultralight pistons, cost about $5,000.00. A roller cam and a rev kit, plus titanium valves and retainers, allowed them to get well above 8,000 RPM reliably. Those little things sounded like a bumblebee on steroids!
Jerry
