Im needing to know if the rear brakes on the 1990 f350 with the ambulance package are the same as a regular dually, and or the single rear wheel 350s, I would like to take the whole backing plate off the housing and swap it out since the current one is trashed, any help?

 

most likely you could find out by measuring the width and length of the shoes and the diameter of the drum. then go talk to your parts man and see if he can see dimensions of the shoes from other trucks.