Yes, it is possible. No, it is not easy.
The *easiest* way to do it would be to take a valid US market vehicle and swap in a solid axle, a engine of your choice (I'd go 1KZ-TE), and then go about looking for the 4-door body. I have seen no less than 5 auctioned off in government surplus auctions (all that were won by scrap dealers and crushed before I had a chance to get to them). I would plan on going elsewhere and finding a 4-door body either LHD from south america or something, or RHD and cut/reweld the firewall.
Here's a tease...
I did the half-cut thing. You can read about it on ih8mud or TDM, I've got a good bit of info on it there. I wish I would have taken the 1ZK-TE that was offered instead of the 2LT-E. Don't get me wrong: I love my faux-lux, but it would have been MAYBE one more day of work to cut and weld motor mounts. The VAST majority of the work is the wiring for the EFI diesel into the US EFI harness. That said, the mileage is awesome (I can count on 28 MPG or so at highway speeds, and I can wheel all day long on very little fuel--maybe 1/4 tank), wheeling a diesel is MUCH better, and the power is MUCH better than the 22RE that was there originally.
It was absolutely worth it. In the 60,000+ miles since I completed the conversion, it has already paid for itself (and I spent roughly $9K total to do the swap). If it weren't for the fact that it's a short wheelbase truck, I'd already have a 4 door body on the way here (or at home already). If I were purpose building it, I'd get an extra cab and swap a 1KZ-TE in and start looking for the 4-door cab and short bed.
The hard part is getting the half-cut (you NEED a half-cut). Importing a body should be really painless, as long as it's just a body. If you cut out the firewall and convert your LHD truck onto the RHD cab, then you have the added bonus of no grey-market swapping of VIN tags. Just some welding and painting.
Finally, here's the goods.
I've got the solid axle waiting for me to finish one of my diesel cruiser projects (not the 45), and that will bring about other junk (like an ARB bumper...)
Or, you can move to Canada and buy one tomorrow.
EDIT--this Hilux resides in New Mexico. I pretty much stalked the owner when I saw it parked on the street. Was brought into the US by a Canadian citizen who was part owner in a mine down here, who then sold it to a US citizen. I realize it's not a 3rd generation truck, but wicked cool nonetheless.
Dan