Not exactly sure what you are talking about as a Cub Cadet 128 didn't have a fuel pump.
I think you should be able to get all the needed electrical information from
http://www.onlycubcadets.net/forum/showthread.php?t=22 and
http://www.onlycubcadets.net/forum/showthread.php?t=27
In order to make this thing work (without major and expensive modifications) you will need to use the factory style starter/generator and a battery. From the wiring diagram simply eliminate the parts/wiring not needed and you should be good to go.
Everything else you need to know about the engine will be in here
http://www.onlycubcadets.net/forum/showthread.php?t=38
Most any NAPA auto parts store will have whatever basic repair parts you may need and our sponsors will have flywheels and other such items.