I am assuming (and we all know what happens when we start assuming things) that we are talking about "Power Pack heads off of about '58 to '67 era as we are talking about the 283 and not the 327, right? Or are we talking about the better '291, '461 "Fuelie Heads" with two "Camel Humps".
Either way a set of professionally ported and polished '291 heads will out flow a set of Vortec BowTie heads that are still in the box (untouched) only marginally and only at high valve lift. Do a little pocket porting and the Vortecs will blow away even thirty year old state of the art heads.
There has been considerable improvement to head castings in terms of flow, and combustion chamber design. I suggest you sell the heads to an enthusiast who isn't interested in performance but wants instead to build a numbers matching trailer queen, and invest that money in new heads.