No, there is not an Isuzu T75.

You really should thing about what Jim is saying. You are correct, your trooper is essentially worthless. It is not going to be worth significantly less when reclaimed from your brother.

In addition to the issues with swapping the engine, you are still working with a 23 year old vehicle. That has to be considered before you dump a reasonable amount of money into it.

Yeah, can you do what you are talking about? Yes. Sure. Is it going to work? Maybe. Will you be happy with the end product? Who knows.

Since the average trooper can be had for cheap, just spend the dollars and pick up a used v6 model and swap a 3.4 into it. The money and time you would spend getting that same 3.4 into a 2.6 chassis can be spent in buying a better base to start from. And, then you get all the electronics and it will all work together very much like it did from the factory.

The 3.4 swap is essentially a plug and play thing into a v6 trooper. Not quite, but close. If you hack it together you will have a) a hacked project and b) something (with a carb) that will not be making that much more power than a healthy 2.6 or 2.8. Why spend the dollars if you are not going to get the most out of it.

Finally, in the end, consider what you really want. Maybe another starting point (jeep, fj40, whatever) would serve that purpose better.

Good luck,
Michael