Hopefully this posts to the right area.
I need to know if a 355 from a 2004 dodge 1500 will work under a 1983 d150 without any extra hastle than just throwing it up under there?

 

Changing my question from a 2004 to anything newer than my 1983 that will already have disc brakes on it that I could just bolt up?
Or... how invasive, complicated, and expensive is it to convert the current drums to discs?

 

I think wilwood makes a conversion for then 9 1/4 but it's not exactly cheap.