I recently bought a 1961 chevy k 10 short fleetside pick up. The VIN and the frame match up. However, I can't seem to identify the motor. It is a V8 with high performance heads (the ones with the double humps on the ends...), headers, old rotten glass packs, and a 600 cfm holley 4 barrel carb. The old owner said that the motor was a 350, but a friend of mine told me the harmonic balancer was too small for a 350. He said it was more likely that the motor was a 327 or a 283. The 283 was the only V8 offered in 61, so i'm hoping that its the motor in my truck. I need to know how to id the motor so i can rebuild it. Any hints or tips as to how i can do this would be greatly appreciated.

Matt