Have a look at Westyss build.
A couple of images showing it folding down seem to have disappeared, but but the basic design images are still there.
Also, the new ATW Global Warrior has a swing down spare wheel arrangement which uses the rear recovery winch. From memory your truck has a rear winch, so that style of system could work for you.
The images were on a different page, here they are http://www.expeditionportal.com/forum/threads/48351-out-with-the-old-in-with-the-new/page15
having the wheel not quite on the ground is not really good, the thing is very heavy to lift off the mounting bolts even at shin hieght, also for me the need to empty out the box that is also mounted on the rack would probably suck if on a trail but I have yet to need to change a tire on the trail.
I would seriously look at the way Jay did the EcoRoamer's spare tires.
With your design you will have to lower the tire, then pick it up off the ground. If you put the tire on the outside of that bar, with a hinge from the top back down to the tire, you can lower it so the tire is standing up. Plus this would make a great Outdoor table when you wanted one. This way the tire just rolls right off and into place, and the flat can roll right back and bolt up.
Is my suggestion making sense? Same mount, at the top put a hinge with a bar (or two) that comes back down to the tire. It would almost be like a swing away tire carrier for an SUV, only mounted no the side.
You would need to make your existing pivot point out behind the truck, but other than that... It seems people are always trying to make a cool outdoor table too, so I thought that was a nifty idea.
I do have one question though...
Your truck already seems to... sag... if you will... in the rear end. Might it be better to put the tire on the front of the truck?
If you continue with the swing up design then consider putting another pulley on the rear just above the top of the wheel when closed. This will not effect the first part of the lift but will positively pull the frame in. You could incorporate it into some sort of locking/anti rub bracket.
I am going to use a vertical lift system using an arm and pulley and my rear winch which is mount between the chassis rails. I want the wheel vertical when on the ground so I can just roll it into position. My 'crane' column and arm will mount on the frame which will carry the spare(s) rather than the camper. The frame will bolt to the subframe and project out just enough.
All designs are dynamic - I usually see a better way or the fatal flaw just as I have started to cut steel and build.
cheers
Every design has its strengths and weaknesses. I had a swing down system on two vehicles and found them VERY cumbersome, esp when on an uneven surface.
This time, I went with the following:
http://www.expeditionportal.com/forum/threads/77493-Fuso-FM260-Rear-Rack-tires-and-m-c
Maybe some ideas for you ... maybe irrelevant.
John