The 7.3 is an ‘89 (although it has a Ford factory reconditioned sticker on a valve cover), believe the GVWR is somewhere in the 13K range (original sticker lost in the cab replacement). Running IAT green coolant, distilled, & DCA2 Napa Kool additive with a collection of old surplus coolant filters, some containing DCA2, some blank (depending on what the test strips say when I change filters). The cooling system was neglected when I bought it, fortunately boiling out the radiator & a new MC ‘stat helped with cooling, and fairly massive amounts of silicate drop-out has been caught by the filters. The bottom tank of the radiator was half full of silicate when I bought it! Amazingly leaks ZERO coolant-but leaks oil from everywhere on the bottom of the engine, RMS & oil cooler mostly.