Re: BBC Heads
The difference in the two heads is found in the size of the valves and the combustion chamber (both have 230 cc intake ports as this was an early design head made from 1978 to '87).
You have a 122 cc combustion chamber instead of the 119 cc found in the '781 and the valves are much smaller and heavier than replacement Manley tuliped stainless steel valves that measure 2.30" intake and 1.88" exhaust. Larger valves would make it breathe better, but the cost to machine the head and replace guides would equal the cost of a new aluminum head to replace it.
Better plan to build torque would be to convert your 454 into a 496 by boring it and stroking it with an Eagle or Scat rotating assembly. That will yield a noticeable jump in bottom end torque. You can surface the heads to build more compression or just buy a rotating assembly with a slight dome on the piston to do the same thing.