will a set of headers off a fox body mustang, fit on my 87 302

 

I would assume they would. Check the head id #. The mustang heads were E7TE models

 

They use the same heads and will therefore bolt to the motor, but that doesn't mean anything as far as clearance from hard parts and having the exit in the correct location to bolt to the rest of your exhaust. There are headers made just for your truck application, if really interested I would look for pictures and see if they at least look similar.