After looking for a couple of years now I finally found a set of the original 3 1/4" TO-30 Z129 pistons. My TO-20 had been rebuilt by a previous owner and it has the 3 1/4" sleeve and piston that they used to offer for the Z120 engines. They only used it to grade their driveway and there was very little wear on the sleeves when I checked them. Plus the top ring height on the Z129 piston is lower than the Z120 piston so the ring couldn't hit the ridge even if there was one. I have found a crank so the only other parts I need to gather is the intake valves for a Z129 since they were bigger and a Z129 camshaft since they were different than the Z120 camshaft. Then I will be able to install the pistons and crank in my Z120 block and I will have the head machined to install the bigger intake valve and then have it milled to get closer to the Z129 combustion chamber size since the Z129 combustion chamber was smaller. After that I will have my wolf in sheeps clothing...lol...because lets face it, as I've said before a TO-30 will pull the lungs out of a TO-20.