Engine is pulled - 273 rebuild or replacement 360 crate?

It is a very nice, clean AZ car that I’ve had a lot of fun with for 8 years. It deserves a good engine and doing it right is my
Number 1 objective. Objective 2 would be keeping is somewhat of a period piece. I’m guessing the motor was done sometime in the 80s so “period piece” is somewhat flexible.

But doing it right and not having to do it again is what the car deserves. It’s been fun and about to get even more fun. If that means a 408 so be it.
I can't wait to follow the transformation !