[Psalm 73]

When I first started working as an aircraft engine mechanic in 1980 we had hundreds of Huey engines shipped back from Vietnam and Thailand stacked up in cans that we would un-can and overhaul.
Just walls of Huey engines!

[Alas Babylon!]

Maybe, but the UH-1N models first flew in 1969. The civilian equivalent of the N’s was the Twin Huey. The USAF did use them in the last two years of the Vietnam war, but the N’s were mostly used by SAC for missile crews. They’re STILL using them.

Is an older, earlier model engine of the UH-1 compatible with the newer N models?

I don’t know. I was just a comms guy. You were the mechanic.