As questions are asked I will post the answers here. Thanks!

Can you walk between the front cab area and the rear box area?

          No, there is no connection between these two areas, for various reasons. Normally, when I use the motorhome by myself, I sleep in the front bunk area, and use the rear camper area as a "day room" for meals and just hanging out. At night, when sleeping the in front I am right in the cab and can start the rig and leave in a hurry if needed (although I have never had to). Further, heating the smaller front bunk in the winter is much more efficient than heating the camper box.
​          When my wife and I are camping together we are normally at established campgrounds with hookups, and we stay in the back with most all the comforts of home; it has a double bed.
          The tractor cab/bunk is on an air suspension; the van box is mounted rigid to the frame rails. Although it has been done, connecting the two areas together can be problematic. (from CRVL 05/16)

Would you mind sharing the costs involved in this project?

No problem . . . .here is a quick breakdown of cost:
          Initial purchase of tractor:                          $30,000
          Frame mods; dropping front axle.                 6,000
          Box installation; rear bumper, etc.              12,000
          Interior finishing.                                             8,000
          Misc stuff; electrical; plumbing.                     4,000
Total.                                                                        $60,000

We purchased the Peterbilt in 2010 when the used truck market was severely depressed due to the poor ecomony. There were a glut of used tractors on the market due to low freight demand and smaller truck companies going out of business. Now, in 2016, the used truck market is tight, especially for the older smog equipment-free engines like ours. Currently, a Pete like ours with the same engine and transmission is selling for $50,000 - $60,000, twice what we paid.

Operating costs have also decreased due to the significant drop in the cost of diesel fuel. When we first got our truck diesel fuel was $5.00 per gallon; now, in 2016 it is selling for just over $2.00 per gallon, and you can find it for under $2.00 in certain parts of the country.

Insurance is $890 annually. 

Routine maintenance (oil change; four filter changes; chassis lube; detailed physical inspection) done every 10,000 miles: $400. 

Repairs are billed at shop rate which at most heavy truck places is $95-105/hr. My truck has been pretty undemanding in the repair category; never left me on the side of the road, yet! Every time I take the truck in for "regular" service I also do a "replacement" item. So far I have replaced the rear brake chambers and air lines; rear axle seals; changed the oil in the rear end and front wheel hubs; replaced the starting batteries; replaced the Pitman arm on the steering linkage; replace the front shocks; and replaced all six tires at about $400 each. 

I have two big preventative maintenance items coming up. Replacing the transmission cooler and replacing the radiator; both are showing signs of near term failure and are leaking ever so slightly. Each will be around $1000.

Here's something to remember about these big trucks: they are built to last a long, long time (1.5 million miles before an inframe overhaul); they are engineered to take a lot of hard use and abuse. But, when it's time to do some repair, it can be expensive. 

I have pretty much been through all my truck's systems and corrected everything which was sub-standard or worn out. Now its just a matter of staying up on things so there are no surprises. And driving it and camping, of course!

This truck is being used so "lightly" now that it is going to outlast me by another generation! (from CRVL 5/16)