[Coley]

You need to decide how important this is to you.
As Led said....there is no such as numbers matching in these trucks...just dated coded motors.
If this is important to you....a '72 truck engine isn't all that hard to find if you look around a bit, noting that there 10's or 100's of thousands of these made.

I had a '72 truck once that had a late 70's truck engine in it...that was do for a rebuild. As it turns out there was a guy wrecking a '72 with its original 350 in it.
I bought that for $150 and had it rebuilt and put that in the '72.....close enough.

Coley