Don't know there would be a huge difference in the overall cost but am just guessing at this stage.
Any views or experience around this?

While there may not be much difference in the cost, the end result is significantly different. Of course, you would end up with a new fresh 4BD1T compared to your worn-out/run-in 4BD1, and the "T" has features that make it a better candidate for a turbo'd engine, however the KLR turbo is VERY noticeably different to the factory 4BD1T turbo; in fact it left me wondering if there was a turbo on the 6x6 at all.
Note too that the quoted installation also includes a dynotune and recalibration of the injector pump to maximise fuel delivery while keeping EGT's low, as well as a custom exhaust. It's not just the labour for the bolt-on.
Go the KLR. I presume you are in Springfield Qld, but consider coming down to Syd to check it out and taking their demo for a test drive. You'll look like this:
