What is the engine intended for. Maximum performance or just a driver. There's a lot of speculation on the topic of zero deck.
I would be concerned more with having a flat square deck surface than anything else.
If an engine has run fine for the past 45 years the way it was there's no need to get all fancy with buzzwords off the internet.
As long as a machinist can do all the required machine work properly and accurate and the engine is properly assembled and properly tuned then you can get another 45 years of use out of the engine.