If its bone stock chances are it hasn't been abused on the trail. I would still crawl around the under side looking for leaks in the drive train components and cracks on the frame. If it has power steering look for cracks around the steering box mounts, pretty common for this model.
The 304 in a 1975 is one of the best. Horsepower started to drop on the 304 after '75. Carb should be a Motorcrat 2100 2bbl. The tranny should be a T-15 one of the strongest of the 3 speeds.
As you stated, rust is the biggest enemy of these rigs.....Good Luck!
'86 CJ7, 258, Carter BBD, Nutter'ed, TeamRush'ed, T-18, Twin Sticked Dana 300, D30 Frt-Pwr Lok L/S-4.10, AMC 20 Rear-Mosers-Detroit Locker-4.10, 2.5 BDS Lift, 1" Body Lift, 33" Wild Country M/Ts, Black Spoke wheels
'45 CJ2A, L134 Go Devil, T-90 Tranny, Warn O/D, T-18 T-Case, Dana 25 Frt, Dana 41 Rear, 531st CJ made
My 401 build: [url]http://www.jeepforum.com/forum/f8/trapshooters-401-build-1338277/[/url]