We have a '78 with a 300, 10-speed RoadRanger, and no power steering, and an '89 with the 237, 9-speed, and power steering.  They both were originally tractors with the '89 being a single axle with a 5-speed Mack originally.  They both will haul 700 bu of corn and pull it very well.  Dad bought the '78 in the early 90's and has never touched anything major on it.  Adjusted the clutch three or four times.  We've rolled both over and had to have frame work done, and no issues.  Around here no concrete company, tri-axle dump company, or any other heavy application used anything but Mack.  No one complained about reliability.  I was telling dad the other day how much I love the way they sound.  When you fire them up they sound like they're gonna move something.