The governor is behind a little cap retained with a bail on the driver's side of the transmission. Unsnap the bail, pull off the cap, and the governor just pulls out. Here is what it looks like. You break off the staked end of one of the hinge pins, replace one weight with one size heavier, and use a #6 finish nail as a new hinge pin, then bend it over a bit so it can't come out. Use the same springs. Reinsert in the transmission and put the cover back on and snap the bail in place. You might want to get a new cover (they're cheap) because there is an O-ring in there and it's probably 30 years old.
What I have that I can mail you if you decide to go this way is the heavier weight piece you need to modify the governor as above. If you go with the 12-235-2 cam, you don't need it. If you go with the 12-300-4 cam, you will need it.
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Confirm 2104 manifold looks right.
Somebody here should be able to recommend a stock-curve HEI here for not too much money. I never had to replace mine, so no recommendations here. Same with fuel pressure regulator.