Another bit of info that might be useful to you:-

The MD-22 is a Perkins Prima engine, marinised by Volvo. So except for the marinising bits (heat exchanger, etc.), it’s the same engine as was used in the BL Maestro, Montego, and Sherpa van. It was also the Perkins P50 marine engine.

Get yourself a Perkins Prima Haynes workshop manual off ebay, and if you need any parts, go to a motor factors (or ebay) and buy Perkins Prima bits.

I got a spare engine out of a Montego for £100 and stripped it down, so have a ready source of spares in the garage.