this is not the easiest information to get to.
i have an 1984 tioga RV (which has the e350 frame and engine), and this is indeed what you have to do to get at the drums.
also, you will need a 2 and 9/16 inch bearing locknut socket to get this sucker off. your average chain auto-store will probably NOT have a socket this large
this is what you are looking for
Bearing Locknut Socket - 2 9/16 In - 6 Pt