It amazes Me that Chrysler bothered to do the heads like Rusty's & the one above with no apparent clue as to how to take advantage of them.
The bathtub head probably destroyed chamber swirl almost completely, & without a piston near-deck to generate squish, They killed what detonation resistance there was then boosted it!!!! As a draw-thru' carb setup, a la early Buick Riviera & T-type, it seems it was doomed at inception.