First, welcome to OCC.......
The snow blades for the 129 were the 42" & 54" that used
IH-549068-R2 Mounting Frame.
The snow blades for the 1641 were the 42" & 54" that used
703-0666 Mounting Frame.
The IH-549068-R2 is NLA. There is no information from Cub Cadet if that part crosses over to the 703-0666.
Personally, I "think" it would, but I can't say 100% for sure.