Following Ron's lead, I've completed my 95 ZJ Tank to 2000 XJ swap and am pleased with the results.
I used a similar vent extension as Ron and went with a 3/8" air gap as my target.
After taking some measurements, I ran a 5/8" drill bit through the tank vent nipple and reamed it out so that the 1/2" copper vent extension tube was a very snug fit.
I heated up the plastic vent nipple with a heat gun and then tapped the copper tube from inside the tank until the ends matched up at the outside lip of the nipple.
The fit was so tight that it required pliers to rotate the 90* end of the copper tubing to it's vertical position, so I'm confident that it needed no additional adhesives to keep it in place.
I cleaned the sending unit and installed the new AEM pump, new regulator and new filters, then plugging it in and tested for power and the float range to ensure that it still generated proper readings from E--F.
I installed a new sending unit gasket and found that cheap cooking spray works great for lubing up the sending unit/gasket matting surface, so that the sending unit slipped right in with a few mallet taps.
Knowing that plastic on plastic fittings are typically high friction and can be stubborn, I applied a liberal coating of silicon spray on the threads of the plastic sending unit retention nut, which made installation a breeze.
With the fill and vent hoses installed, I slipped the tank into place and installed the straps, then dumped exactly 5 gallons of fuel into the tank, primed the pump twice with two key cycles and the Jeep fired right up.
I checked for leaks and then drove 3 blocks to completely fill the tank. I noted that with 5 gallons in the tank, the fuel gauge read 1/4.
The gas pump stopped at 22.1 gallons and I slipped in a little more. Final total was 22.66 gals + 5 gallon can =27.66 gallon tank capacity. :clap:
BTW, I slotted the holes on the passenger side of the XJ tank skid and while it is a more snug fit than on the XJ tank, it does fit, shifting to the passenger side by approx 3/4".
I'm very pleased with this mod and look forward to the benefits of additional range when I drive from UT to CA next month to run the Rubicon.