I bought my 620 new in Nov. 1974. I used to do a limited amount of custom garden plowing/tilling for fellow Church members, friends, & neighbors. I also mowed 2-3 acres for the 1st 25 years until the mower deck was too rusty to continue. I repowered it in 1999 with a 22 HP Kohler Command, before there were repower kits to my knowledge.
Almost two years ago, after extensive use of the Simplicity 48" tiller, apparently one of the bearings seized so suddenly (after I switched the rear PTO