The stock 5 speed KM135 doesn't hold up to the "power" of even a Ford 2.9l V6. I've owned a Bronco II with the same mitsu trans I currently have in my farm truck. It failed as in broken mainshaft after 30k miles of autobahn driving even with 215/75-15 tires. Not Good. There is a reason that Advance Adapters stopped making the conversion. Most swappers change the trans with the motor. A drag race motor is exactly the WRONG motor you want for oofroad unless you're a competition mudder. You need torque not top end power. The Mitsu gears are about 8.8" and can handle 250 ft/lbs and about 200 HP safely but the trans and TC will be straining with 150 ft/lbs, though they will hold up to Turbocharging. Your cheapest safest upgrade if you keep the stock tranny is to swap in an entire Starion turbo motor, harness and ECU.
For my swap, I'm upgrading to Landcruiser axles, SAS to live behind a mild Mopar 318/727/203/205 combo. Yes , the front diff will be on the opposite side with this. If you want to keep the Mitsu axles, I researched this swap: Cadillac 4.5l V8/ S-10 Blazer trans/ transfer case. This keeps the diffs in the stock location. But, once you put on 35's those mitsu hubs are marginal. It's all about balance and reliability. Sorry if I've burst your bubble but dem's the facts.