You are right on the valve size being smaller on the 305 and on these heads the intake port has the ramp so it is good for a low rpm motor and makes more torque. The 350 heads 062 and 906s have the bigger valves and no ramp in the intake ports. The 305 will work great and with the roller cam it will make more power and its easy on parts.Interesting conflicting info on these heads. Looks like a L98 chamber 1.84" intake valve and similar ports to the 350 Vortec heads. It is rated at 230 hp so I would bet the above info is right.