Best way is to buy from a reputable dealer. I am sure there are tell tales that one could look for if there was any doubt - bolts mismatched.... showing signs of being removed... etc.
Easiest way is...do they ask for a "core"? If they do...it's rebuilt for sure. If you are buying a "crate" engine, it is likely new, from the factory, fresh build. Where are you getting it from? I was in the parts biz for many years, and I may be able to tell you just by hearing where it's coming from.
Right...I didn't say that if they don't ask for a core that it is not rebuilt. What I did say was if they do ask for one...you can bet it is rebuilt. Some companies have a nice supply of cores already, or they buy or cast their own blocks new, and use reman internals where possible.
I would think just asking the company you are buying it from would be the easiest way. I doubt a company would stay in business very long selling re-manned for new.
