Here's a photo showing where the engine numbers are. In the center, about a third of the way over from the left edge is the serial number. In this case, it's 6631248. In the center of the picture, you see the type number. This one is 911/83. For a '72, the type numbers are:
911/51 911T
911/52 911E
911/53 911S
As for the serial number, look at the second digit. These will be:
1 911T
2 911E
3 911S
If it's not the original engine, we'd have to look further. Just have a look when you can and see what you find.
Cheers,
JR
