I need to replace the bearings on one of my deck jackshafts. (Model 46562X8)

Take an old bearing oto a bearing supply house... they can measure them up and get you a replacement. (look them up in the yellow pages.)

Things like that are off the shelf items and not unique to your manufacturer.

Hi,
I would probably go with the whole housing assembly to eliminate the possibility of wear to the spacer that is between the bearings. Part #492574.
Did not notice it at first but your headline says it is 42" and further down you say 46"
Here is a breakdown of the 46" machine:
http://www.outdoordistributors.com/pdf/Murray/MURRAY-MODEL-46562X8A-LAWN-TRACTOR-(1997)-PARTS-LIST.pdf
Peace,
Clarke