Does anybody remember mobile engine overhaul outfits?

I remember when I was a kid on the farm we would go to the nearest little town which had a mechanic/blacksmith. If repairs required were more than the guy could do he would have you wait and bring it back when the mobile machine shop was scheduled to arrive. A couple times a year the stub nosed International truck would sit outside his shop for a week or so. I know the mobile machine shop did a rebuild on a 53 Buick for my great uncle and one time we bought a used half block for a Minneapolis Moline from the guy. Seems like he came in the winter so farmers could bring him tractors and trucks to rebuild. That truck must have been pretty full with machining equipment and used parts too.