Welcome to the Green Iron Support Group (our motto...... "we don't need no stinking twelve step program").
Green Iron is addictive....."Resistance is futile, you will be assimilated".
You have fallen into the bad company of good people.
If you buy from the "usual suspects" you will pay premium but the trucks will have been serviced (in most cases) and supposedly checked out.
If you buy from a dealer you will have to factor in shipping....the 813 will take a whole stepdeck to transport....the 818 could share a trailer with a partial load.
I paid over $1200.00 to move my wrecker from south MS to north AL.
You are fairly close to Ted's Trucks in Dothan, AL
'- Teds Trucks N Stuff Store - Military vehicles and parts, milirary surplus items'
I would check with him first....he has a yard full of stuff to pick through.
There are several members that buy to resell......they will prob let you test drive and compare.
Your screen name leads me to believe that you have experience and maybe a CDL.
Unless you are very mechanically inclined or have experience with military vehicles I would do a lot of research and try to make a rally or two before commiting.
We are here to help and you can't find more MV knowlege and expertise on the web than here.