While the Saginaw is a fairly good tranny for light to medium duty use, they do not hold up well to abuse or a lot of torque. If you babied it it would likely be OK........but let's face it your going to rip on it at some time and then have to find a ride home and a tow truck.

A Muncie 4 spd or Richmond 5 speed would be a good choice (but not necessarly cheap ) most used Muncies I've come across tended to need rebuilt in addition to the initial purchase price.

Cheapest and easiest way out for the 454 will likely be a TH400.