It isn't difficult to get within 1 mile of the trailhead without a 4x4 or even a high clearance vehicle if you go by way of the Buttermilk Rd. A Toyota Corolla would do. The last 1 mile is steeper and most people park at the base of the first steep hill as there are good pullouts and nice, creekside camping. Refer to Peter Croft's book for a description of the Buttermilk Rd. approach.
The East Arete as originally soloed by Norman Clyde begins in the notch above the glacier as described here. However it is also possible to begin the ridge at a saddle east of peak 12,241. The ridge leading to the notch includes some wonderful class 3 and 4 scrambling, goes over (or around) a subpeak (13,000+), and then drops into the notch. There is some interesting downclimbing into this notch. Be prepared for a little 5.8/5.9 downbouldering, some very circuitous downclimbing, or else a short rappel. After the notch is reached, you're back on the standard route.
Peter Croft writes: "Clyde soloed the route in the summer of '35, another feather in his cap. However, on his ascent he missed out on the long initial ridge that makes this route so good. Nowadays, if you want full bragging rights you have to do the whole thing."
Jack, I believe you mean the complete route starts "southwest" of peak 12,241, not "east".
A Toyota Corrolla will NOT make it up Buttermilk Rd to the camp spot. You need a high clearance vehicle.
Those roads change over the years. One big hard wet year can make for one muddy mess of a road !