I brand new to the lawn mower scene. I lucked up on 1968 Sears Suburban SS12 for free. Really dont know were to start at on this tractor to build into a competitive puller. It started out with a Tecumseh hh120 engine it wasnt locked but wouldnt start, so I tore the engine down to rebuild with hopefully some performance parts. After man endless searches for parts, needless to say I throwed the engine to the side. With lots of reading i've came to realize what I think would be my best option, that being going with a Kohler engine. Here is were I need the most help, im well aware that no one is going to give up the specs of their winning tractors but all help will be appreciated. Also, is the rearend/transaxle in these mowers worth keeping for a puller or do I need another rearend/transaxle? One last thing if anyone could point me in the direction for the best place to buy engine and/or parts at, it would be helpful. Hope to get some comments and looking forward to meeting some new people.

It is cast iron . Thank you for the input what kind of engine can I get to replace it with that will have the same size crank so that I can use the drive pully that it came out with or will I have to get a diferent pulley made for the replacement engine.