By the numbers you posted it appears to be a model 1806 catalog number 147-640-100 if you can get the serial number which is usually located on the left frame just above the foot rest and you can go to cub cadet.com and they can tell you when it was built and on the mower deck should have a sticker with the model number on it also. The site has almost all the parts breakdowns with part numbers. Beware Cub Cadet has discontinued a lot of the older tractor and mower parts. Hope this helps!
Have a Great Day!
Have a Great Day!