How are you liking the weight of those early hemi heads?
I cut my teeth on making HP on a 1955 New Yorker 331 hemi motor in a 1933 Ford Pickup that had the cab chopped and channel with a very short hand made sheet metal bed
That truck broke a lot of parts (mainly the early ford enclosed drive train ) and whup on a lot of "modern muscle cars" back in the md 1960
As far as filling the spark plug holes in the heads you need to run it long enough for oil to splash in them to fill them, those Milidon sela may help some but the early heads where cast in those heads and the Mildon plug seals need a smooth surface for the O rings to seal up well against, not a real course cast surface
Looking good, I hope it runs as well as it looks