Watch out, it is a violation of Federal Law to remove the emissions controls for a street-driven vehicle.

Given that, does your distributor have wires going to the distributor body (not the cap)? I'm not sure that the 81 Corvettes had "computer controlled" HEI distributors. If they are computer controlled, there is a separate connector that has wires that go thru the distributor body just below the cap lip.

The GM HEI is a very good distributor for street use under 6000 rpm or so. You can get lots of improvement parts for it, if the engine is relatively stock, changing it will not help performance.