Just wondering if there is a transmission for my van that has overdrive. It's a 1986 B350 Maxi 5.9L with a 3spd. Is there something that would bolt on to existing transmission.

 

$$$$.$$
http://www.gearvendors.com/ag3s.html

 

If you can find a 518 tranny from a junkyard, you can do a conversion.
http://www.transmissioncenter.net/SwapInformation.htm

 

The 518 Transmission was the answer for me in getting to an overdrive. I have a 4:10 Differential and run about 2300 at 70mph in overdrive. I researched everything and finally settled on the 518. I control the Lockup, Overdrive, and Downshift with pressure and vacuum switches as my 72 was before electronics. I have two pressure switches which control the torque converter unlock and lockup and the control of the overdrive function. The vacuum switch is used for downshift out of overdrive. I also have installed dash switches to manually control the overdrive and lockup. It works great without the electronics. I have also recently upgraded my old 360 to an 408 which I bought from Blue Print Engines. The 408 is now back at Blue Print with a knock. Will know next week whether they stand by their warranty.