My next crane will be a skyhoist(bought by manitex) rx87 on a tandem. In my opinion if you are going to really load it up and make it a rolling shop it will be overweight on a single axle. Anything over a L55 or sx57 should be on tandem if you plan on loading it with gear and making it anything other then a service truck. For instance, take a look at the thread of the elliot that was at AC sign show. They say that thing is 25k out of the factory. Ad a generator and oxy/fuel tanks and a few tools and you are overweight with 2 people. My friend bought a sx70 and overloaded it on a single 33k chassis and had to have a tag axle installed.
Another person who specialized in manitex/skyhoist/skyhook is the crane center. they are even closer to you. Stamm does top notch work as well as we have all seen.