Or you can go with the 89MM. You lose a gear (4-speed) so the T5 might give you better acceleration. The 89MM was used in full-size GM pickups in the early-mid 80s.
It gives you a .73 overdrive and 3.09 first gear. There were 2 bellhousing configurations, one for Dodge and one standard Chevrolet. Finding a bellhousing for a Dodge box will likely be a hassle. But on the plus side you have the GM 10-spline input (same as Saginaws) and standard fine spline output (Saginaws, TH350 etc.). So fitting shouldn't be any more difficult that the T5. Durability should be as good, if not better.
