I bought my truck in Canada. It was original, if I remember right, the numbers on the engine were original, but the heads were not. A few of the doors have been replaced, and the deal who had it in the UK before coming to Canada obviously figured the LHD would sell well to some Yank, so he immediately had it painted in "respray blue" (as perfectly coined by Briggs when he saw it in real life).
The day I brought it across the border was the day the FBI and CPB was confiscating all those Defenders a while back. So I was nervous that they might be touchy about my frame being galvanized. Even though I had in hand the original receipts for the work from 1990.
My paperwork was in order, the truck was legal, but I was still nervous. It was 95 degrees on the border, and when I pulled up to declare my purchase, the guy barely opened the window on his air conditioned modular office, just enough to wave me into the main building; where after sitting for a few minutes, the next officer looked at the paper work, looked out the door, leaned a bit back in his seat to see if he could get a look at the truck sitting outside (he couldn't) shrugged his shoulders, stamped the paperwork, and I was off down the road.
Not sure what lesson you can learn from this, but just make sure it's clean and original, and you won't have any issues. I know two guys in my area who have started bringing them in from Australia and Japan, and neither of them had any background, and neither of them have had any trouble at all.