fuel sending unit/gauge questions....?

[alec22]

I've recently replaced all the wiring for the dual tanks in my truck. (the PO had cut it all out around the fire wall) I have two new sending units, and they both read only 1/4 tank when the float is lifted to a full tank. Both sending units are new and I get the same reading from both sides even when I switch the units around.

Here's what I've done so far...I've grounded out both sending unit wires and the gauge goes to empty. Disconnect it and it goes to full. From what I've read these are the correct indications.

Now, the sending units that I'm using are listed for an 80-84, and I have an 85. My truck originally had 3 outlet sending units but since all emissions, and the return fuel line, have been removed I decided to go with the two outlet units. The two outlet units only a feed line and a vent line.

Is there something different about the gauges in an 80-84 that wouldn't be the same with my 85? I can only think the these sending units are on a different OHM range then the orginal 3 outlet unit.

I've got a lot of money tied up in two new tanks, fuel tank brackets and straps, wiring, and a fuel selector valve and new switch. I'm stumped and fed-up too!

Please help me!