In mid-2013l, after searching online for months, I acquired a Quigley 2008 cargo RB with the 6.0 and 75k miles for $24k - That was a screaming deal, as I was planning on closer to $30k or more after purchasing a 2wd cargo and doing an Advanced 4wd conversion (I'm in Salt Lake as is Advanced - this was before I was aware of U-Joint, Quadvan, Boulder and Agile's packages). As you noted, $34k is a little on the high end, but with those low miles, I'd probably jump on it if I were in the market in your situation, as boywonder suggested. Ramsey did the RIP kit on it later in 2013, and it's worth every penny! The Quigley conversion is just fine - not certain if it'd be worth spending an additional $10k or more for another full conversion, imho.
Also, like Ramsey noted, all the 6.0's have the need for bulletproofing. The later years do have some improved components (not certain which ones) that reduce the immediacy of a $5k bulletproofing. I installed a ScanGauge right away and watch my oil/coolant temps religiously (anally??, lol!) The delta is still only 6-8 degrees. There are days/weeks/months worth of reading about the subject all over the interweb - the main thing is to be informed.
Good luck - just my 2 cents.
2008 Quigley modified Ford E350 Superduty 6.0l
Agile RIP package with Fox Shox, front & rear
SMB West motorized penthouse
Underfloor Aluminum storage box from northleftcoast
Aluminess Bumper-Mount Spare Tire Rack
Passenger & Driver swivel seat bases
Kenwood DNX572BH Navigation/DVD/CD Receiver