1987 1500 12si bearing question, need advice.

[rfmaster]

GM OE 5 rib pulley should fit 10/12 SI alternator, however you may need to play with a spacer between fan and pulley body. The shaft length is the same on all 10/12 SI units. You'll need impact wrench to get the nut off - I use shop rug to keep pulley from spinning. This way there is less of a chance of damage.

A side note: most CS144 units used wedge style locking nut which requires a whack on a pulley for it release. This style locking system is common on CS144 and some CS130 alternators.

IMHO there is little difference in internals between name brands. Most, if not all get their internal parts from WAI for stock or near stock applications. For 12SI alternator the output current limiting factor is a diode trio heat dissipation capability limited by the airflow and alternator case dissipation. For your 12SI application look for 94 amp, at 9:00 orientation (AC-DELCO # 321-269, Lester #7294-9). You can always re-clock 10/12SI alternator by removing 4 bolts and twisting half's (without separating them!) to achieve desired connector orientation. Autozone gold line alternators have life time warranty and with online discounts can be a cost effective alternative to 'name brands'.

10/12SI alternators are perhaps the easiest ones to rebuild. A complete service parts kit should be under $30 (WAI). The only tough thing to do is to remove pulley and replacing bearings. There are couple video's on youtube that show the whole process.

//RF