It could be any number of engines. The "HC" suffix was used for the following applications:
1965 Full Size 327/250 4BBL Powerglide
1967 & 1968 Full Size 327/275 4BBL Powerglide
1969 Nova, Chevelle or Camaro 350/250 2BBL 3 or 4 speed
Check the casting date of the block to narrow it down.
Ed