Real easy
You need one of these
Surplus Center - 1 SPOOL PRINCE AUTO CYCLE LOG SPLITTER VALVE
Other than drilling some new mounting holes in the valve platform that should do it. The current pressure and return lines just plumb in as they were on the original valve. Next you have to add a line from the return valve and tee it with the line that goes to return port on the cylinder from the directional valve. I don't remember the size of the original valve work ports, at worst you may need a couple steel 3/4 NPT to 1/2 NPT adapters. If you visit Prince's website they have the simple plumbing schematic. If you want I can add a pic later from my TW-2HD.
I would recommend while you're in there plumbing, it's a very good idea and not expensive to plumb a gauge somewhere in the pressure line so you can set the relief and monitor the system performance if you start to have any hydraulic issues.
If you do install the auto-cycle and need to adjust the valve detents, typically the return valve, increase the detent adjustment by no more than 1/8 turn at a time. They're very sensitive.
Adding auto-cycle is one of those additions that will really speed up your splitting time, more so than increasing cycle time with a bigger pump. Throw the two levers and go get the next piece, no need to wait for the splitter. It's a huge timesaver if you typically work alone.
Take Care
