It was a DOHC, 4-valve design, not a hemi, and had shaft driven camshafts and all sorts of innovations. Also, the largest single aluminum casting in the world, at the time.
And it was designed as a V12, not an eight, because Ford wanted to sell engines for warbirds. Problem was that very few people wanted liquid cooled engines and Allison (and Rolls-Royce) had that market locked up tight. So they hacked a third off and marketed it as a tank engine. At least it was so overbuilt that no tanks ever fell out of the sky!
IIRC towards the end of the war they did make a few V12s for tanks, too.