Mike,
The engine is a Perkins 4.236, which was used in Massey Ferguson tractors, at the time when they owned Perkins. There may be a different pulley, but I bet the pump is similar.
I know a chap who runs a business doing tent hire, he finds the Eager Beaver ideal as they are fairly light when using on lawns, etc. He has been scouring for parts as well. Because they were made by ROF, they are a mixed bag of parts, I think someone went to the Ordnance stores and looked to see that suitable parts were on the shelf. :-D