+1 on the weight and what is the expected fuel consumption !(seriously)
It probably weighs around 6800 stock. But add the conversion and the tires it's closer to 7800 or 8000. It should get if running properly 10mpg or so. Add a Banks kit and maybe 12-14. My friend gets 14-16 out of his 2wd powerstroke bus. This is an idi. A tractor motor. Instead of mpg you should be asking about cavatation issues in the block? Is it running the proper coolant and do you know the history or the coolant? On the 7.3idi they bored out the 6.9 and left it with thin cylinder walls. If you don't use the proper coolant it weakens the cylinder walls and causes blown motors. That's the number one and only question that matters on a 7.3 idi. Everything else is real cheap and easy to mainatain and replace. All parts are readily available. It's 60 dollars for glow plugs and 200 for injectors. That goes to 200 for glow plugs and 1000 for injectors on a powerstroke. Make sure this thing has genuine motorcraft (Behr) glow plugs also. No champion or autolite or delco or anything but motorcraft (Behr) zd9 oem glowys.
I am interested in this would you be interested in a crew cab dually diesel? Clean rust free 93 Chevy 3500 6.5td. 2wd has a 16k 5er and a 125 aux tank. All led lights, 179k miles. 5in turbo back and few other things. It's a 93 so it's mechanical just like the idi. No pmd or vacuum pump.
Edit. With the seats removed its neutral on the weight. So maybe more like 7400. Tcase isn't in yet either. Taking out the seats but adding 4wd ,tires,gear etc should max you out around 8k loaded out. And about 7400 as is now with no tcase and no seats but heavy *** tires.