My dad and his dad both retired from John Deere after 30+ years each.
So, to say I'm biased towards JD is a bit of an understatement. I bought a new x300 in Feb and retired my STX38 that was built in 1993. I don't know how many hours the STX logged over the past 18 years but I'm sure it was many.
I love the 100 series mowers like that one, a little bit old school, easy to work on without all the new safety crap they put on the newer ones. Reminds me of the models we had as kids. Good luck with the project and keep us updated.