I made a test bed using a 4' wooden pallet. For the idler gear that hangs down, I bought a flue cap from home depot, cut it in half, and caulked it up into a cutout in the pallet and sat the pony on top and bolted it down. Doesn't leak. I used a 5 gal HD plastic bucket for a cooling tank and sloped the top hose (some HD 1" ID plastic hose caulked into the bucket and the pony outlet.
see video: https://www.youtube.com/watch?v=CPrvvTljREw
Find an extra flywheel housing and turn it into a test stand!
Dont run it very long because the drive gear bushings to the pinion get lubed with oil from the clutch and pinion case. Good idea to use a spare flywheel housing with a clutch/pinion.