Presumption is, that the engine and box were pulled straight from a defunct P38 as a unit and dumped into the defender.
You dont say whether its a SWB or LWB defender, but of a SWB, then there may be some concern over prop-shaft angles and clerences, as well as actual engine / box location on the chassis rails; some of which also apply to the LWB, but as angles less acute, not so critical.
My first concern, though would be the electronics on the engine & box.
P38's are notoriouse for the integrated 'security features' that combined the ECU with the alarm and central locking system. and I believe on later versions, the gearbox electronics are linked into the engine management AND the ABS and if fitted the Traction Control units.
These give seriouse nightmares to owners in P38's where the system is standard, works (or doesn't as the case may be!) like the books and fault finding manual say...
Installed in defender; I'd be intregued to know what had been done to the electronics, and how or IF the integration with the other systems had been dissabled or circumvented. Or carried over; for instance the ABS system....
There is a pottential mine-field of hassles in that one; in fact about 90% of ailments aflicting old P38's multiplied by the hassle factor of having to find them first becouse they aren't in a P38!
Otherwise; mechanical reliability of the engine & box is, well, 'fair'. They have thier faults, but they tend to be reletively easily and cheaply fixed compared to other motors, and the risks are pretty much of a much, and entirely dependent on condition, maintenence or neglect etc.
But in your case, complicated by the hybridisation into a different vehicle.
Putting it simply; I think I'd put it this way; would you, on reputation, buy a P38, and be prepared to take on the 'risks' that those bring; becouse essentially you have a rebodied one, with added potential hazards....
