Proof of new 603 Engine

[TylerH860]

I'm planning on looking at a very interesting SDL this weekend that lacks a service history past 4 years ago. I'll give more details when I look at it, but I'm curious how I could ascertain whether or not a new or re-manufactured engine has been put it. One good sign would be the head casting number, but what else? What does MB, Metric, or others do to make their mark on their remanufactured motors?

The car would be worth it if the motor is as described... less than 30k, but apparently the previous owner did it (2 owners total). During his ownership he's gone through the brakes, rebuilt the transmission, and the AC system.

This is not a likely purchase for me, but since I'm going to be in the area I might as well look.