As Tom said, timing chain is a serious concern. Something to check.
What comes to mind to me, are both the "what to pack" issues, and "how to go about the trip".
Tires. Being 100 miles from the paved, I'd want a spare wheel. Tire plug kit, Fix a Flat, and the lighter socket power air compressor. Tires are a serious concern. Farmer jack might be useful, in addition to the scissors jack. Breaker bar and impact socket set.
The other concern which came to mind is getting stuck. Definitely have a come-along winch, and chain and rope. I've gotten my truck stuck in the mud one time, where I had a tree in the right dirction, but no come along tool. That was embarassing. If possible, travel with another group, and take turns going ahead.
Communication. I'd bring the cell phone, even if you think you won't be in service area. Sometimes you can get a signal from a hill top, or top of a tree. CB and FRS are also good for short range comms. Satelite phone, I've never used one but hear they are expensive but worth it.
Fluids. Gasoline comes to mind. Please buy good gasoline, such as Mobil or Exxon. Nevermind the save 2 cents a galon crap gasoline. And a couple bottles of alcohol drygas. Water, both for you to drink and also for the vehicle cooling system. Oil, and transmission fluid. In a pinch, you can use Dexron II in place of motor oil to get you out of a spot. Dexron II also used as steering fluid. Brake fluid. Couple cans of ether starting spray.
Plan on maybe having to spend a night in a tent. Unless that's already part of the plans. Tent, and multiple ways to light and kindle a camp fire. Lighter, matches flint.
First aid kit. And medications you usually take, plus the ones you don't want to need (pack the pain pills you got after your last dentist apointment).
I'd suggest to post this question to alt.survival and misc.survivalism and rec.backcountry where you will get different (and possibly better) advice than what I've written.
Generally, the part that breaks is the one you left home.