Ford Dodge Toyota Chevy
For Heavy Duty I would say Chevrolet because the Duramax out pulls both Ford and Dodge and the Allison Transmission is legendary and has been proven over and over. Don't let the ford test fool you, they tried to compare there new powerstroke to the older gen duramax and when they compared it to the new duramax chevrolet took the lead again, not to mention the old Ford test Chevrolet was bogged down at 2k RPMs. I think the new interior of the Ford beats Chevy though. As far as the best Diesel motor goes, the cummins get it. They are built to go 600k. Not a Dodge fan one bit though. I don't think you will find a dodge truck over 100k miles that doesn't need suspension parts replaced. Not to mention the transmission problems they have.
http://www.big3diesel.com/64comparison.html
I love my Fords. However, Isuzu flat beds work well because of their turning radius
Pre-1999 Fords turn tight as a drum. We buy them from the county auction. They've been kept up great by the county shop and they usually get rid of them between 50k and 90k miles. (Chris's 96 only had 52k on it!) After two turbos and an engine in my 2004 diesel these F250 gas trucks are a dream.