I have a smallblock that I am trying to figure out..can anyone help to ID this?

Block has long pad behind alternator. 1st set of #'s reads: 15Y150200, followed by a space, then: K 0 28 (the 0 may have a 1 preceeding it, tough to see).

The block casting # at the bell housing area is 3970010.

Underneath (passenger side, freeze plug area) there is a slightly raised long-oval area with: 4 K 15. Just above and to the right of the "15" is A 7
D N

I also noted that there is a temp sending unit on the driver side head. My guess is that this is a 1970's block, not sure. Any help would be appreciated.

Thanks,

John

15Y150200 is the confidential VIN

1 - Chevrolet Division
5 - 1975 model year vehicle
Y - Final assembly plant code for Wilmington Delaware. Made the big cars, Impala etc
159200 - Last 6 digits of the VIN, the 50,200 car built

K 0 28 ?? is the code that is going to tell us the engine type.

K - Engine plant code for McKinnon Ind. (Canada engine manf. plant in St Catherines)

10 - Month of October
28 - Day of month
??? - Engine suffix code

the casting 3970010 is common (millions made) and used on every Chevy model vehicle.