Universal sending unit

[JointTech]

I have a saddletank that has a sending unit on it. When I got the truck there was a valve in the cab to switch between main and aux tank but there was no additional fuel gauge and the dash gauge obviously was connected to the main sending unit.

So I pulled the saddle tank out to have it cleaned and sealed so I can use it in place of the behind the seat firebomb.

when I took it in the guy said ill need a new sending unit. its pretty crusty.

Can I get just any universal unit or do a need a certain ohms to make it work with the factory fuel gauge?

The sending unit has the same retaining clip setup as the normal tanks. Is that part "keepable" and the universals connect inside to it? Or do I have to find a universal with the same locking nut dohickey on it?