There are people WAYYYY smarter than I but I have not had any problem with getting parts from CAT or aftermarket
I watched the owner drive this but I didn't drive it myself. It doesn't have a power shift but do they have a reverser or do you just have a normal transmission.
The 955c is a serie 12a and have a standar normal transmission
If you get to s/n 12A5793 it changes to a D6 size undercarriage.
this serial number is 12A6676