I think I am going to order a transmission from Roadmaster Transmission tomorrow.
They have 3 options.
First is their standard stock replacement for $950 which I was planning on getting but they will only give a 6 month / 6,000 mile warrantee because of the diesel engine. http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7939512601&category=33727

Second choice is their heavy duty version for $1585
4L80E RV, Towing, Plowing Package

Extra clutches added to the high - reverse clutch pack, Upgraded 2nd brake band, High energy clutches by Raybestos used where available, reprogrammed valve body.

All RV stall converters are furnace brazed for maximum efficiency for diesel and gas engine torque.

All RV stall converters give better performance, fuel economy, lower operating transmission temperature.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&tc=photo&item=7939519805&category=33727

And the third choice is the $950 version with the RV stall converter for $385 extra.

Options 2 and 3 have their full 24/24,000 warrantee which includes labor if it goes bad.
The RV converter is supposed to be a lower stall rpm than the oem but I forgot to ask what rpm it is.

It depends on how you drive the truck? Daily driver, easy on the throttle, run empty most of the time, I might go with a stock rebuild. If you run hard or tow heavy loads or climb big hills, then go for the beef! Even stock these transmissions are good.

Not,

Ditto to what Charlie said, but if you arent towing that much deep pan (extra fluid cap) and additional aux trans cooler will add lots of life, if you are hauling frequent or heavy do the HD clutch option do the all as heat is a killer anything you can to to reduce that, is a plus. I went with HD build and aux cool & deep pan my tranny builder said I should never have any tranny worries whatever I decide to pull.

Diesel or gas warranty should be the same, GM makes no distinction between the 2 why should a tranny shop.

They say that it is a heavy duty application because of the diesel.
I don't tow very often but usually have at least a few hundred pounds of junk in the bed.
And no, I am not easy on the throttle. (I like leaving rubber on the road:D )

Also, my truck is the light duty 2500 with 6 bolt wheels and 7200 GVW.

Still should not change warranty period, they can tell if it was abused