I made a deal with my cousin to change his engine. He supposedly bought a 350 that I had to pull out of a C60 firetruck. It appears to be a small block chevy (it had an adapter plate, so that it would hitch up to the monster standard tranny) the harmonic balancer appears to be from a 350 but the flexplate that came off his old 350 doesn't have a big enough centerhole to fit the crank. I was told that it has to have 3 freeze plugs on the side if it's a 400sb (it has 2). How can I tell if it's a 383? Or am I just looking at it wrong?