On the bottom of your fuel tank theres a plug with a philips head screw in it, you can use that to drain the tank when you goto drop it. Just get the fuel level low in the first place then drain out the 1 or 2 gallons that are left. THis helps to not make as much of a mess... trust me... drain the fuel I accidently dumped about 5-10 galls of diesel on myself and my garage floor... (slipped off the jack I had it held on)

There are vent lines on the tank that run through the frame rail... do yourself a favor and go buy the 13/16" short stubby open end from sears. These things will be worth their weight in gold when you are done. Drop the rear driveshaft and disconnect the 3 to 4 fittings for the vent lines at the top of the tank. There are two wires at the top of the tank that goto your fuel sending unit, disconnect them (they are dummy proofed with male / female connectors) don't worry about labeling them.

There are two rubber lines at the front of the tank that you should replace due to age, but remove them to drop the tank. Then, the only thing left to do is to remove the filler neck. I have found that the filler neck can be loosened by getting the clamp right at the tank. Get a 5/16" socket and a long extension and this comes off pretty easily (from the rear through the diff carrier). Then wiggle the filler neck outta the truck (only like 1-2"). Then remove the two bolts that hold the tank in on the straps... Then the tank will just drop, if it doesn't drop that easy, then the filler neck is caught on the frame rail and you just need to wiggle it a little. When you get the tank down a little, there should be a vent line on the top of the tank to disconnect (this ones a pain to get back on).

I have found that if you remove the sending line (the larger metal line) that you must replace it, it will save you ALL kinds of trouble in the long run. There are two lines there, the one in the tank and the one outside the tank, replace both. While you are in the tank you might want to just replace your fuel sending unit. But thats the basics on what to replace, if you want to see the top of a M998 tank let me know I have pics...

As for the '98, shouldn't be much different. But if you find any holes, use JB weld to fix em. I used water to see if I had any other holes when the tank was out of my truck (just be sure to get all the water outta the tank). Infact, some GI wrote on the top of my fuel tank "I got my english teacher pregnant summer 94" and on one of the foot wells it was written, "me and ---- (couldn't read it) are getting married"

Scott
'85 Tan M998