another duster build

well finally got started on the motor yesterday, need to get it to the machine shop and have them check it out, I see a few stamps on the block, and this block was used in 67-75, but im not sure which end of that, i need some new parts for the motor but 68 parts are different than 74 parts from what im finding, theres another stamp on the other side of the block looks like a 2.20.74 is that the mfg date? ive attached some pics as we all like pictures :)20150504_092514.jpg 20160516_155044921_iOS (2).jpg 20160516_155108918_iOS (2).jpg 20160516_155411547_iOS.jpg 20160516_155506814_iOS (2).jpg 20160516_162106485_iOS.jpg