Bad idea. What you have is an old scissor hoist that has a piston pump inside a reservoir connected to a PTO. Depending on the pump it probably doesn't have much GPM but could be OK. Pressure isn't a problem for these (OK to 2500 psi)but the reservoir size isn't large enough to handle additional cylinders and stay cool. Probably is about 12-15 qts based on the lift cylinder size. The valve is likely a 3-way valve for raise/lower/hold. You'd need another(seperate) 4-way valve to operate the wood splitter cylinder, i.e, push/pull/hold/open positions and 2 hoses with quick disconnects somewhere. Don't be fooled by the two hoses as even the 3 way valve have a return port that gets the oil that is from the top of the cylinder stroke when it is fully extended. It could be a 4 way valve but not likely on an old truck hoist. However it will have low PSI on the down side which may not be suitable for a wood splitter system. Engine cooling may be a problem as others has suggested and the old piston pumps WILL NOT with withstand more than 1000 RPM. These units are for intermittant use only and your talking about continious duty.
Bottom line: I would pass and just buy one with an engine on it and save your money in the process. Not a Crazy Idea But Not a Good Idea.

I have been inside a lot of these old systems and the Williams pump is nominal at best.

If you already have a tractor with a 3 point hitch (class II or III) why not just use the lift action of it against a wedge built into a frame with return springs to re-open the "jaws" of the splitter. If your 3 point has down pressure your halfway there and forget the springs, just make the framework and wedge. Very simple design.

1953 Chevy 5-window 3100
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Dave
Engine & Driveline Moderator

If you can't make seventy by an easy road, don't go. ~~ Mark Twain