Yet another 273 build advice thread!

When I was bracket racing my 273 '65 Valiant (pictured above) back in the '70's using the factory stock cylinder heads, I noticed after making a quarter-mile run a few drops of coolant scattered about the engine compartment without signs of a leak anywhere.

Later, when renewing the cylinder heads, we found a very minor crack in a water jacket. Back then, I never paid any attention to casting numbers, so now I can't identify the cylinder head we scrapped back then.