torque converters ?

[Longhorn Man]

I agree, get all the specs, and call a converter company.
You'll need some info on hand, like the weight of the truck, intended use, cam specs, engine displacement, tire size and gear ration along with the tranny model (and possably year)
In reality, a 300 horse engine is just a step over stock, so you wouldn't want much converter at all. I would say in the neighborhood of 1900 RPM... but again, talk to the pros about it.