For reference, the 1M and the King Cat are the exact same chassis. The King Cat has some titanium springs stock, and a 3" pitch track. Other than that, they are identical.
Also, Cat used the same chaincase for....at least 15 years. It mounts in a slightly different place, but it is the same case. The hood/bellypan/bumper stuff is also all the same on any of the ZR3 style sleds (basically most everything from 2001 through 2004, except the firecat style stuff)
If you get a bellypan from something that's not a 1M, you'll need to do some cutting around the chaincase, and get the exhaust deflector if yours is broken. Different engine sizes have the exhaust outlet in different places also, so you may have to do some cutting, but it will bolt on.