problem gets worse when accellerating
when driving i have a fishey smell in cab of truck on 2005 Ford F-250 Super Duty
What engine you got? I don't guess someone has played that old fish/sardines on the engine trick on you have they? It's been done before!! Amongst friendly pranksters that is, just a thought.
That fishy smell could be antifreeze from the heatercore or a leak..