500 bucks??? Where's the Jeep located? If you don't buy it someone else will and fast! I'll buy it if you pass it by.
The 304 is a great engine. It's very under rated. It's a good comparson with the small block Chevy.
As far as what to expect? What do you want to do with it? The sky is the limit as to what you can do with the Jeep.
Just make sure you change the oil/filter, check all the fluids before you start the engine. Take a can of WD40 and shoot a little in each spark plug hole for some needed lube. The cylinders have to dry after 5 years of sitting.
Good luck and keeps us informed.
80' CJ7, 360 Howell Injected, 3" single exhaust, NP435 4spd, Dana 300 AA clocking ring, Currie twin stick, Tera-Low 4 -1 kit, Dana 44 front, cut 10" wider to 63", 4.10 gears, ARB, Yukon axles and Super H/D u-joints, Currie Dana 44 rear, cut wider to 60 1/2", 4.10 gears, ARB 35 spline, Currie 35 spline axle shafts, 2 1/2" x 11" Ford drum brakes, CJ-SOA conversion, Tom Woods F & R drive shafts, Warn 9500i winch, 6 point cage, Homemade F&R bumpers and tire carrier, 1" body, Pro Comp supension Kit, 12.5x35x15 BFG's, 15x10 OMF beadlocks, Body armor, OBA.