B model... IMS, self-sealing tanks, but not crashworthy/breakaway connectors/port. C model bumped fuel capacity, and D was the stretched troop carrier that saw fuel tanks moved around a bit. H had self-sealing/crashworthy tanks, break-away, self-sealing connectors, and the pull-through filler port.
Accident was close by in WV, so got calls from former unit buddies within an hour or so. Definitely a tragedy all around.
Common to hear old Huey jocks opine that when the last UH-60 went to the boneyard, a UH-1 would pick up the crew. Sadly, last Army/USAR/NG UH-1 was retired in 2016, so that smug mug that the Skid Kids practiced never got used.