I appreciate your feedback and assistance in finding a head gasket for my Cat 30. Olson's is working with me. My machine has been modified a lot. There are no serial numbers that I can find. I believe it to be an early to middle series 30 tractor. All I have to go on is that I have the small spring for the front idler sprocket, the Y-shaped manifolds and a single head. As a last resort, I will mail them the home-made gaskets that I took off. Thank you, Dale Rainwater