Yep the tubed Dodge. I'm using a totally different drivetrain in the buggy (Chevy).
I haven't run Flat Iron Mesa. From the Red Rock 4 Wheeler's site:
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Trail Rating: 4
Flat Iron Mesa is south of Moab and is bounded by Kane Springs Canyon on the north, Hatch Wash Canyon on the west, West Coyote Canyon on the south, and Highway 191 on the east. A main road has a BLM sign, but our trail leaves the highway earlier (18 miles from town) and it quickly gets 4WD status on numerous old trails that reach fine canyon overlooks and provide some interesting four-wheeling. Most of the trail is fairly easy; the "4" rating goes with only a couple of obstacles, some having easier bypasses. There is a harrowingly narrow section on a cliff edge that barely allows a full-size vehicle to pass - being small is a comforting advantage. The Easter Sunday run will be in the reverse direction, giving it a difficulty rating of 4+ and requiring differential lockers. Approximate mileages: 55 total, 17 off highway.
Scenery: There are views of the La Sal Mountains, local cliffs, and different canyons throughout the trail. The cliffs and canyon walls near Kane Springs and Muleshoe Canyon are especially beautiful. Hatch Canyon is about 700 feet deep at the overlook where West Coyote Creek joins it in a series of cascades.
Road Surface: Much of the trail is two-track on sandy dirt that is occasionally dusty and is always inlaid with bedrock. There is a little slickrock, a gravelly hill, and numerous rocky ledges.
Obstacles: Several short hills won't be done on first tries by everyone. A long climb to a flat-top butte is in a loose mixture of coarse gravel and dirt, and it is made more difficult by a few large rocks. It can be bypassed. Near West Coyote Canyon overlook are a long ledgy downhill (site of a tip-over a few years ago) and a narrow shelf that requires a tight turn. (Note that, on Easter Sunday, "down" becomes "up" and vice versa.)
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What about behind the rocks? That's one of my favorites and it really only has one difficult obstacle, but there are plenty of optional ones. Rusty Nail is also a great trail.
Ryan