Can't find "SUN" SBC suffix code. Help decoding, please

[nikwho]

Hello all,
I'm trying to decode an engine that my son and I are building. It's believed to be a 1980 350. Casting #4010207
Block suffix code V0216SUN (Flint, MI Feb 16th, I gather) SUN?
Crank #932442 (I'm not forgetting a "1" @ the beginning. This is how it's cast)
I cannot find a partial VIN anywhere. And this block was recently cleaned up and vatted, so it's pretty clean.
It's got a really nice 4" standard bore. The nicest original bore I've ever seen.

Any help would be greatly appreciated! And, I do not have this engines original heads.

Thanks much!

Nik