Only two tanks were ever used in the YJ, a 14.5 metal tank, and a 20 gallon plastic. 14.5 metal was only used 87-90 and then phased out. They did not ever limit the 20 gallon to 15 in 87-90, that was the purpose of selling the smaller metal tank. Whatever tank you had then, was your capacity. Everything 91-95 is plastic, Most of the 91-95 were limited to 15 gallons so that Chrysler could sell the 20 gallon mod at an upcharge. If you opted for the "larger gas tank", a technician would go pull the vent tube and they say they would change the sending unit to the 20 gallon model as well. However, both factory 20 gallon owners and the 15ers who upgrade their tank to the 20 capacity say it sits on full for a long time, and in my case it does as well. Not sure what the difference between fuel sending units would be if they both sit on full for a long time when the tank is 20 gallon capacity. You would think the 20 gallon unit would adjust the gauge to go down evenly rather than sitting on full for 5-6 gallons, I thought that's the whole point of the sending unit swap. Who knows.
For what it's worth, when I pulled my tank, my sending unit did have a "15 gallon" sticker on it's wiring loom. Never got pictures of an OEM 20 gallon to see if it had a sticker or not. I know the Mopar sites show different part numbers.
As for the pumps, there were two styles. I've always been told that one style was for export, and one for domestic. The smaller one for domestic. I was also told that when US sales went up, they started using the Jeeps built for export to the US market, so some US folks ended up with the bigger fuel pump. I really can't confirm that though. Seems like the odd, hard to find large fuel pump usually comes in the earlier years and the smaller pumps are pretty much the only thing you'll find in the later years. My 94 had the smaller pump, so I got a Bosch 69544 replacement.
You probably don't need to change the floater assembly. If you have any inaccuracies in your gauge, it's usually due to the fuel bowl in the tank being warped, not from an actual issue with the sending unit. I only changed my sending unit because I really didn't feel like messing around with changing the pump in my stock unit. Was just easier to buy new. My MTS unit came with a pump in it so I actually didn't use the Bosch Pump I received. so I kept the Bosch as a spare, am running the MTS, and have the factory unit & pump bagged up and stored "just in case". It was working perfectly fine so I certainly am not going to throw it away.
Not really sure what to do with my old tank, it has a warped fuel bowl but is otherwise in good shape. I went with a brand new MTS tank to go with everything else in that project.
