I haven't started the big build yet, but so far what I have is a good running 18HP Kohler out of a newer Craftsman mower. Of course I plan on keeping the electric start and gauges and all the goodies off the mower and building a "dash" of sorts on the splitter. I have an I-beam, and a 5" x 30" cylinder that would be right at home on a splitter, and I'm planning on building it to be a horizontal and vertical unit, with a small hydraulic cylinder to raise and lower it to and from the horizontal and vertical positions. I think with that heavy of a beam and that large a cylinder, it would be a killer to raise and lower it manually.
So I have just about everything I need except a pump, control valves, and all the hoses and what nots. Of course I'll have to take a few pictures when I finally get around to building, I know how you guys love pictures!