This is for 340 builders

Press fit works well for stock and lower output motors that do not require frequent disassembly for freshening up. Their main advantages are simple assembly, cheaper pistons (no locks or extra machining) and they rarely come loose. In performance applications they require extra clearance to prevent pin scuffing.
Only draw back is some times the spring locks break and the pin slides out. I had a 383 that this happened to and it sure cut a nice key way in my cylinder.