Study this & follow the links in the caption:
The 1" filler hose that Steve shows there for your '91... had fallen off and
was inside in the rear tank on the '91 F150 I inherited. Don't know how it
got that way, there was talk about they were -going- to drop the tank on
it but I don't believe they had yet. It had only 66k miles on it.
Wasn't any harder to fill than the rear tank on my '75 F150 I bought new.
The '75 F150's been a friggin' pain to fill from the very first day. :(
The trick to it is to park with the truck tilted-away from the pump and to
also tilt the filler nozzle 20 degrees or so either direction from straight up.
I don't bleed blue, YMMV on that? ;)
Anyway, my Bronco doesn't have the 1" plastic-filler-hose either because
it'd gotten damaged from throwing the tread off a tire before I got it. The
parts truck's 1" filler pipe was screwed up too etc so I ain't got one on the
'91 Bronco. It's not that big of a deal, for me, since the Bronco takes fuel
a little bit better than the '75 F150 I've had for ~38 years. :)
If -your- trouble is because the filler hose fell off, then just know your '91
Bronco takes fuel -better- than the Ford-designed-it-that-way-early-
dent-side-pickups. And be friggin happy about it! ;) LOL
Alvin in AZ