Hi spences66six,
One small point, all of the above posts assume you use a "progessive" carb., i.e., Holley-Weber 5200, Weber 32/36. The throats in the Weber 38/38 and the Holley 2100 / 2300 series open at the same time, i.e., "synchronous". The progressive carbs are good for mileage as the small throat is all you will use until the throttle is open 70%+. These carbs also help low rpm torque as the keep intake manifold velosity high at low rpm.
Just to help your planning process, the Holley 5200 and the Weber 32/36 (DGV series), are the same carb. Holley built the 32/36 under license from Weber. Best place to get one is Stovebolt. You will need and adapter, best one is Clifford. Your 66 came with a "vac only" advance distributor so you will need to get a dizzy with a mechanical advance (sometimes referred to as dual advance - 68-73 stock with "single vac advance") or DSII with single vac. I see you have the Pertronix system (I like mine), maybe you have the dual advance dizzy (mechanical + vac advance) already?
Steve