Funny thing is is I believe that's what I have too? The story I got was from the previous owner and they said they worked in a wrecking yard and pulled the motor and transmission out of a Pursuit car. It was a 318 with 360 heads and a 727 transmission. When I looked the numbers up on the 318 block it came up "race block" Doesn't have R. I'm sure it's just a factory remanufactured block or something.