I know of a kid that has a 6spd manual ford and beats the crap out of it and it hasn't broke yet. Im pretty sure that the Torqshift is the same as the allison. I also know of a seriosuly modified ram, I don't know the specifics, but it runs 11's. =o
Yeah, Ford has the TorqShift transmissions that seem pretty nice. It has a pretty slick tow mode. If I get a Powerstroke, it'll be the 7.3L or I'll get a 6.0L and change the injectors and put in a new EGR cooler if they haven't been done already to solve the problems they had.
I want a Dodge with the MB G56 6 speed manual, those can really take a beating. Although an upgraded clutch would help a lot.
Watch out for the first generation duramax. Im pretty sure they have head gasket/ head issues. The Allison transmissions in the chevy/gmc can take a beating. I think the Fords have the Allison too, but call it a different name.
Really any turbo diesel would be fine. As long as it's newer than 1995 and isn't that old awful GM 6.5 turbo diesel.
My dad said he'd prefer it be a Dodge Cummins or a GM Duramax because of how reliable they are. The limit is of course price, but I plan to work my ass off this summer ;)