That's a pretty heavy application for a transmission that was designed to be used in cars and some 1/2 ton trucks. I don't think I would do it.

I saw one at a swap meet last weekend. The guy wanted $250 for it. At that price I would want to open it up and do a close inspection of the internal parts. Also make sure the shifting solenoid works.

There is some part on the overdrive that interferes with a floor shift linkage. I don't remember what it is now. There is a way around it detailed in one of the Chevy truck restoration books but it's not very elegant if I remember correctly. This is for the Borg-Warner(Warner Gear) unit. Didn't Saginaw later make these also(synchro first gear)? Not familiar with the Saginaw unit other than it's supposed to be possible to take the overdrive and put in on the back of the Saginaw four speed(sure would like to have that setup!).