Buy it back if you can no matter what, you'll find an option that works for you.
I would take it some where capable of checking the frame for damage.
If at all possible, make sure it still runs and drives, (kick out the windshield & vacuum the seats) and basically checking for any accident-related mechanical issues that may not be readily seen.
Option 1:
If there's no frame damage, body swap it. When the body is off the donor, inspect it for rust, damage, etc, address the problem areas and when the interior is stripped out, add
sound deadening and spray it with an
insulating coating (I prefer
DIY Lizard Skin), add some inside the doors too.
You likely need the dash wiring harness because the gauges will be specific to the diesel, since both will be LHD this should be much easier.
Address any known maintenance items on the drivetrain while the body is off, but don't go too far down the "while I'm in there" rabbit hole, just get it together and working. Worry about the suspension and bumpers later. The faster you can get it driving, the more it will feel like progress and less like an albatross.
Grab all the good stuff from the wrecked interior that non-US models got.
You'll be able to make a decent amount back from selling the gasser drivetrain and the usable body parts from the wreck.
You may want to take both vehicle titles to the DMV, they will likely title it with the VIN from the body donor.
Option 2:
Drivetrain swap, gauges (and or dash) swap, fuel tank swap (look into fuel tank coatings as now would be the time to coat it, or move to a
long ranger tank). The situation regarding the fuel lines (supply and return), I'm not sure about but likely MUD members here know.
Option 3:
Fix the body - IMO this only ends in two ways A. mis-fitting doors, rattles, squeaks, leaks, etc B. A really really expensive and/or time consuming process.
I owned a body-swapped LHD diesel 60 (Canadian diesel drivetrain with a US gasser body) that the previous owner had swapped. We loved that truck but had to sell it because we couldn't get it back to the US (it had nothing to do with the body swap).
I would recommend option 1. and discourage option 3.