I found a small overdrive after looking for more than a year to put on my 59 1 ton and its a .75 over. Looks to bolt right up to my sm420. The model number looks to be a 2091 and its just a direct and over. All I have is the box and I'll have to make my own shift lever. It has no govener or solinoid. Very basic for an overdrive.
As for brakes -
www.praisedynobrake.com has kevlar brake shoes for your truck (I have them on mine) and that with new drums up front will make your truck stop very well. I didn't want to loose my 1 ton rating or make a lot of mods up front. This was the easiest and cheapest solution even if the brake shoes were a bit pricey. My front drums were also out of service limits, and I still had them work very well.
I say go for it!
You can also get a 4.10 gear set that plugs into your rear pumpkin very easily to get speed up and you can also put on big big tires which also help. I did both of those things first. The OD will go on when I get did with my 72 project.
