About the only way is to contact Country Clipper. And yes it from the 1990's. From what I can find several different Kohler CV engines were used. Or it might take tearing the engine and measuring the cylinders. Luckily most major engine parts are the same for say CV23 series.
BTW the problem you have ran into is common with Kohler engines as the decals tends to fall out after several years. It is recommend that any equipment owner record all the equipment numbers they find on their machines. I do it here as a business of repairs and it has save me several times in the last 10 years. It is good that my Auto Manager software allows the storage of these numbers.