Is there a junkyard gem slant six combo?

i don't know the magic recipe of which head is the best, which bottom end has the most compression and/or best pistons and rods, but that seems to be the direction you're heading which is excellent.

i will however strongly encourage you to run something other than the 1920's, anything other than them suckers. or at least build your manifold so that it can accept another carb when you tire of fussin' and fightin' with them god forsaken things.
I'm probably using the 67 pistons, just assuming more compression. But I'm looking for insight on block, head, crank, rods, etc....

What's wrong with the 1920 carb? It's been several years since I ran one, but I always thought they were about the best 1 barrel ever put on a slant. Only one that ever gave me trouble was on a 72 Dart I had, 69K one owner miles. Going to work one day, it decided it wouldn't run less than half throttle. After a rather "interesting" ride the rest of the way to work, I tore into it on my lunch break. Dirt in the bowl, holding the needle open. And then looked at the fuel filter, or more precisely, the lack of one. Factory one use clamps on all the connections. Apparently, it slipped by the guy installing filters on the assembly line. And it took it 69K miles and 28 years to decide to be a problem, lol.