Q1 Did you guys run the entire Niagra Rim trail?

No, there wasn't enough time, since we didn't get to the trailhead until about 3pm. Also, some parts of the trail were more difficult than we were willing to take on, given the lateness of the day. We did scout out a major portion of it, though. The trail has many "entry points" or bypasses. Basically, a graded forest service road runs nearby along most of the trail. There are various intersections along the trail where you can easily get to the bypass route.

Q2 What was the elevation range?

6900-8100 feet. The paved route (at the developed campground) ends at 6900 feet. The highest we got was 8100.

Q3 Did you see any campgrounds?

Yes.
1- Niagara Rim OHV campground, run by the forest service, is developed, and is located at the end of a paved route, just 5 minutes from the highway. It has 12 sites, pit toilets, picnic tables, and firepits (no fire permit required). No water or trash services, though. There's a nice creek that runs alongside the campground. Cost per site is $6. Some sites can accomodate as many as 5 or 6 vehicles, while others can probably fit only 2. No per-vehicle fees.

2- Many undeveloped sites on the actual Niagara Rim 4x4 Route. Primitive camping, no services; pack it in, pack it out. Fire permit required. No fees. As long as you're not on the road or on a sensitve alpine meadow (which are clearly marked) you can pitch a tent.

Q4 Is it possible for more than 5 trucks (or however many trucks that would participate)?

Most definitely, yes. In fact, the area offers a variety of trails suitable for 2WD, stock 4WD, and all levels of modified 4WD.

Here are my pics

Track Log

Pros:
* Huge network of trails to explore in that region
* Trailhead and developed campground is ~3.0 hours from San Jose
* Developed campground is 2WD and RV-friendly
* Developed campground is less than 20 minutes from hard-core wheeling
* Low campsite fee ($6, no per-vehicle charge)
* Wide range of trails suitable for all experience and equipment levels
* Primitive, no-fee camping easily accessible
* Great scenery

Cons:
* Easy access means this trail system may be crowded
* Access to trail requires travel via Hwy 120; Yosemite traffic may affect travel.