They were so low on horsepower back then because it was the early stages of vacuum diagrams, smog equipment, catalytic converters, etc. What I'd do:
Good 4bbl intake and Edelbrock Performer carb (600-650cfm, no bigger), then swap the cam when you can. Go to www.summitracing.com-
get the intake/cam combo, most likely the Performer RPM, and get the Edelbrock carb to match. Then, start on your exhaust; either free-flowing cats or take advantage of the grandfather clause and ditch them entirely, good free-flowing 2.25" inlet / 2.25" outlet mufflers (I'd recommend MagnaFlow [Flowmasters are overrated]), and have an exhaust shop weld it in using 2.25" piping. They may try to push you on 2.5", but you'll need the torque provided by the 2.25" to really get that beast moving.
Let me do a little more searching before I tell you anything about cylinder head swaps.