Ken, it's a 1966 327/275 with a Powerglide and a Holley carb, from a full size passenger car. The block was cast on June 17th, 1966 (F176 probably), but you need to verify that assembly date (T0574). That would be May 74th!. Also, that's a month before the block was cast!
Recheck the numbers again and let me know.
Ed