Check your glove box for these codes. I'm only listing the GM RPO's for alternators 100 amp or higher here.
8A7, KG8 - 130 amp
8A3, KW2 - 124 amp
8A5, 8C0, K98, KG9 - 140 amp
8C6, KG3 - 145 amp
8C7, KG4, KG5 - 150 amp
8W5, 8X5, K61, K62, K65 - 105 amp
8Z3, 8Z4, K60 - 100 amp
K09 - 120 amp
K63 - 110 amp
KG7 - 125 amp
KW1 - 160 amp
KW3 - 135 amp
KW7 - 170 amp
KW9 - 190 amp
KYU - 200 amp (