Doing some digging the engine and car came from Skinner & Co. with (0.420"/0.436", 219degrees @ 0.050"). I drove the car in '06 so it still had that cam.
He discusses adding headers and then high flow heads before changing cams https://grassrootsmotorsports.com/forum/grm/non-traditional-racers/36089/page1/Granted a 318 isn't a 273 but just trying to provide some perspective. For street and autocross it was a good setup. And it fit the rules for a the vintage race class Skinner set it up for on the west coast.
Side note: I'm convinced that the bearing clearances, oil pump, and temperatures are too cold for 20W-50, but Dave is not (yet). 50 has some advantages for road racing but the bearings have to be built for that, etc.