The axle in the truck you are looking at is more than likely a vacuum shift if it is two speed, it was an option for 1.5 ton. The gear ratios will be slow and slower. Not sure what your plans are for the truck, but if you want to go fast you don't want a two speed, or even an old axle. Something newer that was available with faster ratios would be a good idea.
An adapter is probably hard to find or non existent to match an IH trans to a Chevy. Are you sure the trans you were considering is an overdrive? With some careful measuring and machine work it may fit if you try hard enough.
Think about what you want the truck to do, then let us know. Your answer will help us advise you as to weather axle and brake swaps are worth the effort or not. While you figure what you want to do with the truck this site may help
http://www.drivetraindirect.com/t_gear_calculator.htm Grigg
