I did it kind of mix 'n match. The pump, control valves and drive to pump lovejoy coupling I got from Surplus Center, the harmonic balancer insert and pump drive I got off this site. IIRC, the whole magilla probably ran around $400, but that was a few years ago. My tractor has an AD 192 instead of the 203, so my harmonic balancer was a hair small for the drive insert. I had to buy a used balancer from a 203 and have the seal surface machined a hair to fit through the engine case, so that added a couple of extra bucks.
You have to cobble together a sump out of 1/2" black pipe and bore a hole to modify the pto shifter cover plate for a fitting. Helps if you have a torch to heat and bend the pipe to clear trans innards as required. I just ran the return to the top cover.
Pretty easy job, just takes a little finaglin'. Hardest part was cutting the front weight rack accurately for the shaft drive and pump mount to keep the pump and drive shaft aligned properly.
If you do a search under "Massey 65 Front Pump" you'll find a ton of info here. Increases the utility of the tractor quite a bit insofar as using a hydroswing haybine or a round baler.