OEM plastic 20 gal tank there are not any direct fit replacements. You can get new sending units for them, but if you need a replacement tank you'll have to find an original used one. There ARE aftermarket 21 gal tanks, but they don't fit the factory 20 gal skids.
You can also get aftermarket skids (Kilby, for one) for the factory 20 gal tanks, but again, the 20 gal OEM-style tanks themselves are not available new.
85 CJ7 258, borla header, Team Rush, MC2100 ,optima batt, Warn 8274, agr super box 2 & pump, T5 w/ B&M shifter, centerforce 2, superior 1 piece axles, warn hubs 2.5 in lift, 31" BFG MT
85 CJ7 258, A/C, T176, MC2100, Team Rush, Warn XD8000i, superwinch hubs, 3in lift 31" BFG AT/KO