The 2 barrel heads are ok for the street.Maybe upper 400's hp with the right parts, after that I'd go with the 4 barrels heads. The intake valves measure 2.05 on the 2v and 2.19 on the 4v. (I believe). They are both big.
73 was the start of the big time pollution motors, so you have to change cam,intake,carb,timing set, and change the rockers over to an adjustable roller set up. The rockers on that motor are notorious power robbers.
It will never pull like a 460 but it should be respectable.