[midniteblues]

In either case of stepside or fleetside the reverse lites and tail lites ground too the bed.
Besure all the mounting bolts and mounting areas are clean tight and rust free from the bulb socket too the bed mount.
Common problem on fleetsides is rust between the bed and light fixture where they mount in the pockets.

Then you need too make sure your bed is grounded too the frame and that connection is clean and tight.

Reverse lights on a hidden toggle switch is a good way too forget too turn them off or not even use them in the first place both not good.
A micro switch mounted securely too the shifter body or the oe setup is best.