2bbl to 4bbl guidance please

[Jeepnut]

1968 C10, 327. I have been led to believe that the motor is original...now I’m doubting it. Block is 3914678, MA suffix. This returns to a ‘68 from a car, with a manual trans? (Truck is AT) The heads are 3973478, J141 date code. This points to a early 70s 350? It does have the 5/8” spark plugs. Plausible that early in its life it received a head swap/valve job(?). Current 2bbl manifold is 3919801. At issue is...trying to decide if I should remove the current 2bbl and swap on a 4 bbl...only because the current 2bbl is trash, a cleaning and rebuild didn’t help much. Thought about switching to a 4bbl but only if the heads will support it and if it nets any performance and driveability gains. Or just buy a quality rebuilt Rochy 2bbl. Thoughts?