I voted 5 speed manual of course! like dieselcash said, nothing better than changing gears!
I try to DD in my 91 gasser. it gets great mpgs, is cheap to maintain, and has inexpensive 15 inch rubber. for a daily driver, the 5LM60 is a great transmission. nice even splits. first is high for towing, but it can be done with the surprising low end torque of the 4.3L v-6.
The NV4500s are better suited for trailer pulling, as the 3-4 shift is annoying when driving around, but 3rd is so much lower that it makes a great mountain pulling gear.
the SM465 is what it is in my 91. like the 6.2L that twists it, it isnt anything fast, but it is dead reliable.
everyone should have one manual transmission in their fleet IMHO, wheter its a car or truck. It just brings back simplicity, and it takes your mind off of things.
4 speed sm465 in the 87 crew cab dually that i FINALLY got back from the shop (yes i hate having others do the work on my vehicles and they screwed this one up bigtime), 7-8mpg
I got the NV4500 in the DD. I would almost rather keep the low miles on the diesel and drive the white mule. Even with the SM465 it wont get over 12.5 MPG though.
SM465 is the stirdiest tranny I have ever had, almost 700K miles between me, dad, and my uncle and alot of farm/surveying work/stump pulling and only thing changed on it is the input shaft seal twice while the motor was out. If the Massey Fergussons won't pull it you the the white truck.
5 speed manual in the 86 Dodge Ram 50 and 5 speed manual in the 88 F250, both used as DDs. I only have a 4.3 mile commute to work each way, but its a 30+ minute drive in traffic, I love manuals in traffic so i dont have to keep my foot on the break