Tank if I recall is in the step up to the cabover.
Remove the staples/screws that hold the front wall of the tank step in place, carefully separate the paneling from the frame behind it so you can find the anchor points for the frame.
Remove anchors, remove front step/tank compartment wall. Disconnect all plumbing connections to tank (Most should be hose clamps), remove tank.
Replace tank, its polypropylene plastic and its **** near impossible to mend, reverse process to rebuild step, avoid drilling into tank in future.
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'1992 Dodge W-250 "
Dually"
Power Wagon - Club Cab Long Bed 4x4 V8 5.9L gashog w/4.10 Geared axles'1974 KIT Kamper 1106 - 11' Slide-in'2006 Heartland BigHorn 3400RL