1973 340 detuned?

Don't believe the specs you read online. Stock J heads are 65 cc's-ya right. I've been messing with Mopar's for over 30 yrs. and if there's one thing I've found it's you can't go by advertised specs.

If you do change pistons you better weigh what's in there and find pistons that weight the same (or really really close) or you'll need to have the rotating assembly balanced