In the seventies, I helped move Cat 651B's all over Wyoming. It was a common practice then. We used scraper dollies, or roaded them when it was a short distance. As I recall, the Dolly's were made by Cozad of California, but Trail-King might too, or they may have been made by some one else as well.
In 1971, I watched as the now defunct Holloway Construction Company roaded their 651's up from Southern New Mexico to Cherry Creek Dam by Aurora, Colorado. There were about fifty of them altogether. They came right up Interstate 25, took them three days to make the trip. In 1970, on my way to Albuquerque, I was run off the road just outside of Cuba when two Kiewit 651's came barreling around a tight curve towards me. They were taking their share of the road out of the middle. Fortunately, I had a small car then and was able to squeeze by.
By the late seventies, roading heavy equipment had become all but impossible as most states by then were demanding all kinds of permits and police escorts. Most would not allow roading any more, scrapers had to be moved by truck. I was still able to move some 777 Cat end-dumps from Hellertown, Pennsylvania to Easton. We took the back roads and made the move very early on a Saturday morning. In Kentucky in the early eighties, I moved Cat 773 end-dumps on back roads fairly often (that was all eastern Kentucky had then, way back roads), and was never bothered. But that's just how Kentucky was then. I also roaded Cat 992 Loaders from Stewartsville, New Jersey back to some town over in the eastern part of the state. Went right down I-70 all the way at slightly less then 25 MPH. No permits, didn't even call the cops on that one.
On one 651 move in Wyoming, we took 6 of these brutes down I-25 from just north of Buffalo to thirty miles north of Douglas. We used a Wyoming trucking outfit, now defunct of course, and those boys wanted to "get er done" quick and go home!" They were out of Gillette as I recall. I was bringing up the rear as an escort and the last scraper had been delayed by a flat tire, which the driver and I changed as fast as we could. Once we got moving though, that driver wanted to catch up with the rest of the herd and he floor-boarded the throttle.
Pretty soon he was clipping along at over 60 MPH, and the rear tires of the scraper were about as wide as a car tire and ballooned out to the point they were smoking against the fenders. I called him on the CB radio and suggested that unless he wanted to buy a pair of new 39.5X39 scraper tires, he better slow down to about 30 MPH and stop at the next rest area to let the ones on the machine he was dragging cool off. I've never seen since that time, scraper tires stretched out as much as those two were.
He did slow down, and when we pulled over finally, I couldn't touch the tires as they were too hot. We sat there for an hour and then continued on our way. We caught up to the rest in Casper where they had stopped at Wyoming Machinery's yard. I figured I might lose one or both of those tires on the job, but they never gave me any trouble.
My boss at the Buffalo Job recalled a time when they had to moved about a dozen 651 scrapers in Pennsylvania from one job to another. They decided to road them, but as a precaution, he bought a dozen sets of Cat 631 decals and covered over the 651 decals on the scrapers. As luck would have it, they got lost in some whistle-stop town and had to pause at the State Police Station to ask directions. The desk Sargent went out to see what was making all the noise and he just whistled and gave my boss the directions he needed. They couldn't get out of town fast enough he later recalled! That would have been about 1970.
Good luck on your search.