Although the R50 is a lot more machine than your M3, Gleaner has made lots of better machines than the 40 & 50 series rotors. The cab is the same as what you now have on the M. It was passable in its day, but the 62/72 is heaps better. The little P3 processor machines like the 40, 50, 52, 60 have a shorter rotor and thus are stretched for seperation capacity. The air-cooled Deutz can also be problematic. They are a marvel of an engine but must have been kept meticulously clean by the previous owner and you; if you happen to buy it. Cooling fan must have also been watched carefully and have been replaced when cooling started to suffer. They do wear out and the consequences are dire for whoever happens to own the machine when the cumulative effects of neglect show up. Deutz parts are extremely expensive and even no bargain when you find aftermarket jobber parts. Then you need to have the ability to work on the little jewel of German engineering. It isn't difficult, but its different than the water cooled diesels we're used to.

My advice would be to keep looking until you find a Cummins powered 62/72. Likely won't be a lot more money but will be a lot more machine.