i have a 94 chevy silverado C1500 Ext Cab ..im trying to figure out which master cylinder i have . i guess in 94 the Company made like 4 types of the master cylinder . my repair book doesnt show which 1 it is . my local parts store doesnt know . so i was wondering if anyone can tell me which unit i need by looking at the VIN# that would help alot . 2GCE19Z9R12648**