Putting a GMC 6 together from a pile of loose parts can be a challenge. They all have the same rod length even though 270 and 302 blocks are taller. There are 2 wrist pin sizes and two notch sizes on rod inserts. There are basically 4 heads. two styles of rockers. Not sure of push rod length but it seems like there should be two. A few parts are the same as 235-261 Chevy six. Chevy & GMC crank & timing gears can interchange all the way through the 250--292 and even the 153-181 4 cylinders. Lots more I can't remember it all and may be disremembering some. I good running Jimmy is a kick to drive.
