I'm Mitch and I'm looking forward to discussing the dozer and it's components! Honestly, I don't own a dozer, but I do own a Speeder with the exact engine in it, well, maybe its about 98% similar. I look forward to providing some info as well as getting some feedback! This should be fun!
So far I haven't needed parts myself, however I've heard great things about Jobbers Inc. I'll paste the link at the bottom, right now it looks like they've got a cam and some pistons for the FC. I'm sure they could locate something, though, depending on what you need.