Does anyone know if the frame mounting brackets for the engine are different between the 4.9 6cyl and the 5.0/5.8L v8's?

Thank You.

 

Of course. The V8 is only 4 cylinders long, so its perches are only 2 cylinders away from the firewall, behind the front crossmember. The I6 is 6 cyl. long, so its perches are 3 cylinders forward, on top of the Xmbr. The rivets holding the perches on the frame can be removed (as described in the caption of the diagram below), and others can be installed.