If you can't get any help from the part store call Fleetwood and just maybe they can give you a direction to go in. I know Fleetwood of today isn't the same as it was (new owners) or go online to workhorse .com, I bet they can help .
Welcome to the forum Everett. Fuel regulator for a 1988 454? Not ringing a bell for me. Are you talking about a fuel pump? Any parts place should have a fuel pump if that's what you are wanting. Give us a little more info.