Started missing like it was a gasoline engine before it died doing 70 mph.Can anyone give me some ideas on what to look for?

 

Welcome to the site..

How many miles on the clock?
Many things can stall a 6.0.. Actually any late diesels.

First,, any CEL prior or during the misfire and stall? Do you still 'hear' the fuel pump run on a key cycle to ON? Been running fine other then the stall? Could be fuel related, HPOP or a drop in PSI delivery, FiCM, and a host of other engine management items. A scan tool that can look into the PIDS and display normal (or fault) values is a huge help in determining what's up. And check for codes for some sort of direction.

First step would be fuel, move forward from there.

 

Thanks Hayapower,
185,000
Didn't get to check anything.Was on the way to work yesterday.Had it towed to the Dealer.
No news yet.
Didn't think a diesel would miss like that.
Brought it to the Dealer last week for being hard to start and they come up with nothing!