I have a 1963 427 which had it's mains enlarged back in the day, it was a common practice especially among center oilers in the 70's I bought the thing recently and it has 10k miles on it and was running a Melling M57HV
oil pump. It got 65-68 pounds of
oil pressure at cold start up but when it was hot it would drop to 18 at idle, in gear it's an automatic.
I installed a M57HP (high pressure) pump and I now get 100 cold at start up and 25 at idle in gear. Now 25 is fine. 18 was probably ok. It is hard to watch it drop from cruising speed to idle though.
I wouldn't do it if I were building an engine.