I'm proud of you MagicRat. I expected you to reply, "there's no such thing as a good diesel"
The SAE patterns are not like corporate patterns, so the #3 isn't a chevy style thing. The SAE standards for bell patterns were established to make things easier for the genset manufacturers to match up their powerplants to the generators, and it caught on in the 60s to include medium and heavy trucks, marine, and agricultural applications.
Here is a picture that might help with identifying SAE patterns:
