Inspect the torque rod ends...
Inspect the torque rod ends on the rear tandem axles. Small cracks in the rubber are no big deal, but missing chunks and rotten or soft rubber are bad news. If worn or damaged, the ends or the entire link will need to be replaced.
Options
The M35A2 trucks never came with luxuries such as power windows, power door locks, air conditioning, or power steering. If you're looking for this level of comfort you're buying the wrong truck. Although there is a bolt-on Air-O-Matic air-assist steering kit available from Inter Agency Motor Pool. Most trucks came with canvas soft tops which are typically in ratty condition. Trucks with steel tops and trucks with winches bring a premium price since they are the most desirable. You're better off taking your time to find the truck you want. Trying to make the wrong truck right will cost you more time and money in the long run. That is unless you have the space and time to stockpile and sell non-running parts trucks. Ultimately, if you want a M35A2 with a winch, find a truck that has one on it. If you want a truck with a steel hard top, find one that has the steel top on it. But hey, if you're into projects and don't mind the extra expense go ahead and build your dream truck. Companies such as Boyce Equipment, Government Liquidation and Memphis Equipment can supply you with all the parts you need to install a steel or fiberglass top or a winch.
Inspect the knuckle boots...
Inspect the knuckle boots and steering components for damage. Most of these parts are easily replaced and not very expensive. It's very rare to find a spotless truck like this. Some oil leaks are normal, a real gusher is not.
Testdrive
If you can, take the truck for a test drive. It should start right away. If the engine needs to crank-over more than a few seconds it could be worn and have low compression. Once started you'll need to let it warm up. Watch the oil pressure gauge; it should slowly climb to 60-75 psi. It takes a little while for the oil to circulate through the engine block so give it plenty of time before mashing the throttle. Also monitor the air pressure gauge. No air pressure means no brakes. Hopefully the low air pressure alarm still functions. There should be about 1.5 inches of free play in the clutch pedal. If the clutch engages near the top of the pedal stroke and or it feels like it's slipping it may need to be replaced soon. If there is noticeable slop in the steering it can typically be remedied by tightening the draglink ends or replacing the draglink if it's worn beyond adjustability. The truck will be loud, but listen for any unusual noises. Some gear whine is normal, but hissing air and loud knocking are bad signs. If the owner claims the fuel pump has been turned up, you'll notice increased power and more smoke from the exhaust stack. But if the fuel pump has been turned up, the truck should also have a pyrometer installed in the exhaust manifold just before the turbo. The exhaust gas temperature should not be allowed to reach 1,400 degrees for more than a few seconds or engine damage could result. Test the air-shift transfer case mechanism and transfer case levers as well to make sure the truck is shifting into 6x6 and Low-range.