I'm having trouble finding .020 pistons and while I was waiting for some to come back in stock I was looking through "How to rebuild your Nissan & datsun OHC engine". The pistons in a 79-83 in a look to be the same as a 75 other than the rings, but I could be wrong. Will ITM RY6140-020 pistons fit? I have a n42 block and head. Thanks