[Heater63]

Mike,

Santucci's book "Chevy I6 Power Manual" lists your 473483 block as a 250cu in made from 66-79. This block did not use an integral head (which yours is not from how you describe it)

Fred T is right on the date codes. Which, is interesting, in that if you can't tell the decade with only one digit! Your CON number is J148, so it was cast October 14, but could have been 1968 OR 1978 !! The numbers by the distributor pad give info on the exact build, compression and excessories, etc, but I don't have anything to decode that.

Hope this helped,

Heater