98, if you have the K&N part number I think you can cross reference at
http://www.amsoil.com/amsoillookups/MasterFilterCrossRef.aspx or use this chart:
AMSOIL# K&N# Product Style Flange Type Base OD (in) Flange ID (in) Media Height (in) Top OD (in)
EaAU3050 RU-3570 Round Tapered Center 6.000 3.000 5.000 5.0
EaAU3051 RU-3580 Round Tapered Center 6.000 3.000 5.000 4.0
EaAU3090 RE-0810 Round Tapered Center 6.000 3.000 9.000 5.0
EaAU3555 RU-3550 Round Tapered Center 4.625 3.500 5.500 3.5
EaAU3560 RE-0950 Round Tapered Center 6.000 3.500 6.000 5.0
EaAU3570 RU-3130 Round Tapered Center 4.625 3.500 7.000 3.5
EaAU3590 RE-0920 Round Tapered Center 6.000 3.500 9.000 5.0
EaAU4075 RF-1040 Oval Tapered Center 9.000x5.750 4.000 7.500 7.0x4.5
EaAU4090 RU-0870 Round Tapered Center 6.000 4.000 9.000 5.00
EaAU4091 RC-5102 Oval Tapered Off-Set 9.500x6.750 4.000 8.938 9.0x5.5
EaAU4095 RC-4780 Round Tapered Center 6.625 4.000 9.500 5.25
EaAU4178 RC-4900 Round Tapered Center 7.375 4.125 7.875 6.625
EaAU4510 RF-1024 Oval Tapered Center 9.250x6.250 4.500 10.000 7.0x4.5
EaAU4560 RU-3480 Round Tapered Center 5.875 4.500 6.000 5.0
EaAU6065 RF-1042 Round Tapered Center 7.500 6.000 6.500 5.0
EaAU6075 RF-1041 Round Tapered Center 7.500 6.000 7.500 5.0
EaAU6080 RF-1020 Round Tapered Center 7.500 6.000 8.000 5.0
EaAU6081 RF-1044 Round Tapered Center 7.500 6.000 8.000 5.0