Shields1, welcome to the forum,
Of all the open bowl 613's I've ever found anywhere totaled maybe three, two had blown engines, and the rest of the machine was far worse, I figured entire new drivelines before they were operational and those were in your part of the country, and one almost new one auctioned off in California for almost 30k, otherwise in over five years looking, that's the total I've found. Several dresser 412's with open bowls, but like you said, narrow for government specs, that and parts are hard to find in my area for them. I kind of stumbled across the terex I have on the east coast as well, not bad shape everything considered, other than old and needing some minor repairs.
I like the size for smaller jobs, really handy for what we use it for, wished I have a few more but eventually I'll stumble across something affordable worth taking home.
I've also found a few elevator versions of the 613's where the mechanical elevator was so shot they took them out and did a makeshift conversion for an open bowl, can't say I was impressed, seeing how the rest of the machine was taken care of about as well as the elevator system, but I guess some do whatever it takes to attempt to get the job done.