Since the connector is underneath the body, it may be worth it to spring for "marine grade" heat shrink tubing.
West Marine will carry it, along with Amazon.
Don't know if it is, but if that is the same connector on the top of the rear tank, it is a lot of work to get to it.
(don't ask me how I know)
-= John =- 1985 F-150 EFI 302/5.0L dual tanks, long-wide bed, "heavy-half"