Patrick's used to sell Venolia forged pistons and still may. The Venolia pistons have domes specific for the GMC heads and you can buy direct from them also. Verify your forging numbers on the rods to make sure all rods are the same and don't assume they are original to the engine. After 80 years of existence, anything could have ended up swapped and changed in it from mechanics just trying to get the vehicle back on the road. My Sealed Power book shows the evolution of the changes in connecting rods and the big pin was common to both the 270 and 302, since those two engines were the only ones remaining at the end of the production years. There are several different forging numbers for each style of rods produced, so if you're still in doubt, just get your machine shop to confirm the ones you have.
