Frank, While not truely Rare, they aren't under every bush anymore.
The engine is a Buick 350 so parts are readily available since that engine was in the Jeep trucks/wagoneer for several years asa well as the Buick cars for many more. But it's not the same as the Chevy 350 that's available EVERYWHERE.
The body parts are a bit harder to find now. The front half of the trucks and wagoneers (the original full sized versions, not the wannabe XJ-Cherokee version) was identical from the mid 60's through to 91 (last year for the Grand Wagoneers), so I can get body parts from any of those that I can find. There is a small outfit that makes replacement panels for the beds and other parts too, but they are more expensive obviously.
Axles, tranny and transfer case were all Dana if I remember correctly, so while improved versions came around later, they are damn tough.
Since there;s nothing complicated involved (no computer, no AC, no power steering or brakes), just a bare bones Truck, there's just not much to it.
I've now even been told that the hub I need was the same one used on the CJ's of the same era, so they shouldn't be hard to find if I mess this one up.
That's what Kaiser was known for, Taking the best parts available and blending them together into nearly indestructable vehicles. 1970 was the last of the Kaisers.