I would really like to use my still good fuel gauge on my '56 f-100, but I have taken out the stock tank and unit and put in a '66 mustang fuel tank. Is there a converter or something that I could get to make this combo work?

 

I did somewhat the same thing with my '48 panel. I used a tank from a diesel truck and my stock gage. At the time I modified the tank to fit the panel I didn't realize there was going to be a problem with using the newer tank's sending unit and the stock gage so I just moved the location of the sending unit hole, which is smaller than the panel's stock sending unit. I found out this spring when I hooked everything up that the gage pegged out to "F". I rigged up some resistors between the tank and gage and also installed a shunt resistor between the posts of the gage. The values aren't exact, you have to experiment to find the correct values for your set up but I think I put .5 ohm resistance in the line from the tank to the gage and rigged up something like a 20 ohm resistance across the gage.

To test the setup's accuracy I placed the sending unit on it's side and wired it to an extra stock gage I have and adjusted the sending unit to "E", 1/4,1/2,3/4 and "F" and got fairly accurate readings. I know the gage isn't 100% but at least I know I have fuel in the tank. When it gets down to 1/4 tank I put some gas in it. I also know there is about an inch or so of space between the point my sending unit float hit the empty level and the bottom of my tank so there is a little insurance built in.

As far as I know there is no kit made to remedy your situation. Most everyone will tell you to change the gage or find a compatible sending unit, which is the best, and easiest way to do it but I wanted to keep the stock gage and I should have made the tank accept the stock sending unit but I didn't want have to screw around with draining the tank, flushing it out so I could cut and weld on it and then cleaning it out the debris from cutting and welding and then re-installing the tank. I just thought it would be easier to futz around with the electrical.

 

I bumped Bobj49f2's post on the sending unit and gauge to the top. Look at post (stiock gauge/modern sending unit). A very interesting post with a lot of good info. Hope this helps.

Gil