I also agree there's another problem.

I have a lockup torque converter behind a 3.0L that's probably putting out at least as much torque as Kevin's turbo - somewhere around 220HP/260lb-ft. I understand the heat-creating sustained highway slip on the non-lockup units due to weight and aerodynamics, but I drive my truck hard in the lower gears where there is no lockup. The additional torque created by the roots blower at low rpm surely puts a lot of slip on the 1-2-3 gears and I often thumb-shift the A/T to avoid the 3-O/D upshift until I'm above 4000rpm. I frequently hold the shift points until 4500rpm on hard acceleration, creating opportunity for heat buildup due to slip and reduced airflow cooling at lower speeds.

Before the blower was installed, I drove the truck (heavily loaded) from SC to Colorado and back..... with 32s.... at speeds consistently above 80mph..... on severe grades.... with a non-lockup transmission. If there was going to be a heat issue, I would have seen it then.

You might pull the temperature switch and check the accuracy. If you've installed a body lift, have you raised the radiator so it gets proper airflow? Are your radiator cooling fins clean? Is your radiator clean internally? Is your complete cooling system in good shape? It may make a difference which way you route fluid through the cooler - have you reversed the hose connections to the cooler?

Frank