Thanks to a great  detailed site  I have found an image of the awning/shade tarp that he used while camping with a Toyota Tacoma. (He also has wonderful instructions on modding a Tacoma for wilderness travel.) The tarp I have in mind is bigger (it is a 12’X20′ white tarp here). That size should add room to have a flap in the front and some wind protection.  Thanks to Bob’s blog I found that painter extension poles would work for cheaper poles. The attachment method, bungee cords hooked onto the wheel wells, is the way to go.

The tent below is an interesting addition. Why would I need it? Thats why I have a bed in the truck, no? And where would I store it? For sure I need the tarp.

update:

After 5 years on the road I finally have a good solution. The big tarp eventually leaked and it became very heavy as I grew progressively older. I switched to a very lightweight tarp.
After 4 months of use and abuse the light weight tarp wins the award.