Bluebeard,
jefe here. I live about 32 miles from you down Hwy. 20, 3 miles past White Cloud on the west slope. While we did not face your similar dilemma, we did go the direction you are headed, namely a SRW, 4WD truck with a short bed/small hard side camper that will occasionally travel narrow dirt roads. What overhead obstructions are you facing on the way to your claim? If it's less than about 10 feet 4 inches to clear, you might consider a pop-up camper on a 250/2500, 4WD truck. Beware that quite a few pop-ups weigh more than the smallest, narrowest hard-sides, but they will clear at about 8 to 8.5 feet in the down position. Especially if you are only going to use it a couple weeks a year, do go for a petrol/SB truck. Also, with that little time spent in it, it makes little difference if it's a pop-up or a hard side. We've spent more than 200 nights in our hard side Lance. near Bishop:

2500 to 3500 trucks in CA are considered commercial so you pay a lot more for registration than with a 1500. Also, Truckee is the coldest place in the continental U.S. (maybe not this year) so I would get a gasser as diesels would need to have the block heater plugged in below about 05 deg. F, which you get to on occasion.
I own a short bed Dodge with a camper with the smallest platform Lance makes and the whole thing is a couple inches over 20 feet long so we can park in a parking lot or along the curb with abandon. Lucky for you, there are a lot of truck campers in our area (within 200 miles) and I see a constant stream of candidates passing thru Craigslist CA. Be sure when you are looking at prospectives you go thru all the motions of living in the thing:
1. Lay on the mattress for at least 10 minutes to see if it's for you.
2. Go thru all the motions you would do in the head. And it is a head as in boating for most people. Sit on the pot, grab the wand to take a shower. reach for the toilet paper. open the cabinet and pull out something. Can you stand easily in the bathroom? I'm only 6 feet tall and must crouch a bit to fit in there. But I'm used to it. Coming from a much larger RV, make sure you have NO claustrphobia. Jeanie and I have none. Not everyone is destined to accept all the pros and cons of owning a TC.
3. Turn on and off all the controls to make sure the heater, water pump, stove, fridge, and check the fittings, plumbing, seams, climb on the roof and check for recent weatherizing. Check around windows and doors for any leaks, current or past. Is anything broken or in need of repair?
4. Alright. Send me a PM, and I'll go looking at prospectives with you. I have nothing to lose and you are close. You have everything to lose. I'm not trying to talk you in or out of owning a Truck and Camper. It just needs to be a good fit.
regards, as always, jefe