My relay was under the hood, we have a box of relays up there. But the R50's may be different than yours.
I know there is a panel under the cargo area, on the floor, that allows you access to your fuel sending unit and all... (in the WD21's)
Next time you start the truck, turn off your radio and all, then just turn the key to accessory, and listen for a quiet buzz from the back, that would be your fuel pump.
Again, try a search for these terms, as I know there is more info on these boards than in my head on this subject!!