This is straight from ZZP on most any belt you'll ever need...
Stage 2 IC
685 - 6-rib, 3.3"+
680 - 6-rib, 2.90" - 3.20"
08-685 - 8-rib, 3.0" - 3.20"
08-680 - 8-rib, 2.60" - 2.90"
Stage 3 IC
680 2.6-3.0
685 3.1+
25060721 72.625" stock bonneville
25060716 72" for 3.4" bonneville
25060670 SS IC with 3.2+ SS IC
4060660 - GTP/GS/SS supercharged with 3.2 - 3.5" pulley
4060650 - GTP/GS/SS supercharged with 2.9 - 3.1" pulley
060716 - Bonneville SSEi with a 3.4" pulley
060670 - ss IC with a 3.2"+ pulley
060667 - Stock GTP or ss IC with 3.0" pulley
675 - Gen 5 blower S3 core 2.3"-2.55", Stage 2 core 2.4"-2.60" pulley
060680 - ?Stage 2 intercooler 2.6 - 2.8" pulley
Gen 5 blower S3 IC 2.6"-2.9", S2 IC 2.7"-3.0" pulley
060685 - Gen 5 blower, stage 3 IC 3.0+ pulley
?Stage 2 intercooler 2.9 - 3.1" pulley
060915 - Stock accessory belt for '99-03
-also works with either UD WP pulley or OD alt pulley but not both
060923 - Accessory belt for 99+ with UD WP pulley and alt UD pulley
060905 - Stock accessory belt for '04+
060935 - Stock accessory belt for 97/98 (94")
060938 - Accessory belt for 97/98 with underdrive pulleys
060970 - SS M90 for 97/98
060950 - SS M90 for 99+
915 99-03 stock accessory belt
923 99-03 for underdrive water pump and Alt pulley
905 04+ stock accessory belt
935 97/98 stock accessory belt
938 97/98 for underdrive water pump and Alt pulley
667 stock S/C belt for GTP, GS, SS
658 GTP, GS, SS S/C belt for 3.5-3.25 pulley
650 GTP, GS, SS S/C belt for 3.2-3.0 pulley
721 stock Bonneville SSEi Supercharger belt
716 Bonneville with 3.5-3.25 S/C pulley
875 99-03 accessory belt with Meziere water pump
864 04+ accessory belt with Meziere water pump
895 97/98 with Meziere water pump
685 S/C belt s2/s3 ic 3.0-2.8 pulley (depends on tensioners)
680 S/C belt s2/s3 ic 2.7-2.55 pulley (depends on tensioners)
670 S/C belt ss ic with 3.2+ pulley
667 S/C belt ss ic with 3.2-3.0 pulley
