I wast thinking the same, how hard can it be, get and engine and gearbox from a 156, use the EPR parts disc to cross reference driveshafts etc and sorted,
but then
what about the fuel tank and lines
and the engine loom
instument panel, I doubt the diesel revs to 7000rpm
radiator will have to be swapped
ECU, therefore immobiliser, therefore keys etc etc
engine mounts
and this if it fits in a RHD installation (apparently it does, but who knows)
and that is why people fit LPG instead!