Those are pictured in all the factory brochures, but are actually pretty rare. I've got one that's going into my '67. I removed the in-cab tank, welded up the filler hole and installed the in-frame auxiliary tank, which will be used as the primary.
Any time those show up on E-bay, they get a pretty penny.
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-O-----O- Keith
'67 F-100 2WD SWB ~ '69 F-100 4WD SWB w/7" chop ~ 1975 F-250 Ranger XLT Supercab Camper Special My '67 restoration video -> Posting and you!<-a MUST watch for all!!