You own a camper and have the bad luck to own one with a knackered T4 engine. And the FI system's AFM has probably worn out too. (I still believe it would be possible to provide a mapping from a modern MAF sensor to the AFM input on the old ECU..) A Subaru conversion is a good swap. If you have a knackered T1 engine then the advantages are less clear as you can get an all new one for less than the price of a T4 recon.
I made a small start tonight. Battery disconnected. Carb is off. Dizzy out to be sent off tomorrow. Some tin ware removed. Basically items from the top half of the engine. Gaps filled with rags. Will do some pics next time.