M-880 manual transmission

I have a 1976 M-880. This has a factory 4 speed manual transmission. I have put 170,000 miles on it and need to replace or rebuild the motor. I would like a little bit more power and would love a overdrive. What's out there to do what I want. I was thinking of going with a 360 or having the motor rebuildt and modifed to get about 10 to 20% more power. What kind of overdrives are out there and their prices?

I think m880s only came with the 727

http://olive-drab.com/idphoto/id_photos_m880.php

This may be one of a kind. I bought it from the Army and I have been the only private owner of it. The base I got it from is a really isolated base in Nevada. They had a Technician who worked there who was intitled to have a M-880. He was the only one on the base who was. So instead of going through the expense of shipping one truck to that base they gave him authorzation to buy it from the local Dodge dealer. This has all the original government data plates. You might know the base it is Herlong.

I highly doubt its a M880. For one they all had Automatics. The Government bought other trucks besides the M880's. They bought plenty of club cab and crew cab trucks but none of them have a M designation.

The quickest way to get more power is from a 360 but this requires a 360 flywheel and they can be kinda hard to find. 360's are external balanced while 318's are internal. One of the motor mount brackets is different from a 318. Oil pans are also different along with the front damper. The only transmission to consider for OD is the NV4500. They came out in 92 dodge trucks and were used to about 2000 model year. Can be pricey. Has to be from a 318 or 360. Can't be from a Diesel or V-10

Probably more cost effective to buy a wrecked or salvage later model rig with a 5.9 Magnum with a 5 speed (2500 or 3500 rig). This will give you everything you need plus fuel injection. You will probably spend double trying to find a 360, get an NV4500 seperately, make the tcase work, etc.

Skinny is correct. I forgot that the NV4500 Won't work with the 203 transfer case. Would have to use a 241 or 205 transfer case. And then somehow but locking hubs on front axle. Magnum 5.9(360) flywheel is different then the 71-92 360 LA flywheel also. They are both external balance engines but at different amounts.