340 coolant in oil

I should ask if if it is a 4.07 bore in the block? (4.04 +.030 340) It would measure just a hair over 4-1/16. I ask because of what looks like 2318 piston number... i hope I’m not bombarding you with too much at once here, I didn’t get the weather I hoped to have here so I am unable to work on my own junk today...
No, I appreciate all of yall taking the time to come up with ideas and suggestions. The casting number on the heads looks to be 3418915C it also has the letters AAWJ and 360. The pistons are L2316 .030 over. Another thing I noticed when tearing it down yesterday was that the distributor was loose, you could easily turn it by hand. So did yall think the gasket looks to be ok? I've only owned the car a month, I bought it from a kid who did not know much about the motor. He said it had recently been rebuilt and had a "cam" put in it. It does idle like it has a stout cam in it.