gear vendors o/d?

[Myoldtruck]

Ok so my truck I using for towing sometimes, and do some highway driving. I found a complete sm465 trans with a older gear vendors o/d unit. comes with bell housing, shifter, and high/low range switch for the shifter. I can pick up for 1300.00 for everything.

What would you do?

I would end up with a extra trans that I could keep as a spare or sell outright for about 150.00.

Im looking at the gas mileage savings and wear and tare on the engine. this is my everyday driver. truck has a 3.73 open rear.