Here's what I can find from the info you posted, going to the Cub Cadet parts site.  Your deck assembly number is 190-301-100.  The spindle assembly number is 603-0835.
The MTD spindle number you posted 918-04394, has been superseded to a 918-04426.  I don't know how you found that number and it may fit your Cub Cadet, I have no way to do a cross reference that number.  Don't know if this helps or confuses things.