I dont know if they will interchange but I have one off a 98 that has a little rash but is funktional and could be made to look good with a little work if you are interested for cheap($20 + shipping)
Clutch Case? Do you mean the right side engine crankcase cover Secretsix? If so I'd have to say the answer is yes. According to my Honda parts fische the part number for the right side engine crankcase cover is the same for both the '98 and '02 engines. 11330-MW4-020. What's kinda screwy though is that the part number for the crankcase cover is the same and yet the part numbers for the crankcase cover gaskets are different. 98 cover gasket part number is 11394-MBG-000. '02 cover gasket part number is 11394-MCW-000. Go figure. It could be that the older part number will simply just update to the newer number though. :unsure: I've noticed that Honda tends to do that.
it should fit. the engines are of the same block and basically all they did for the 6th gen was add all sorts of tech to the 5th gen. as for the differences in the gaskets, my bet would be that honda found a better material (or cheaper) for the gasket.