I have a 91 LE with a faulty alternator, i bought one from an sse at the junkyard, but it wouldnt work. There is a different connection for the power. I still got it to screw in there. So my question is how many differnet alternators were there for the 87-91 bonnies?

You did get a replacement alternator from a bonny, olds 88, or a lesabre in our years, right? It should hook up though. You didn't bend any pins or anything, did you?
Perhaps exchange it for another unit, or have your old one rebuilt. You could also use the connector off the donor car too, could you?

it was a replacement from a 87-91 bonneville sse, i fit the connector in.

to my knowledge theres only one replacement alt for the 87-91 and its a 105 amp. maybe the alt you got is just defective.......

Most auto parts store chains are able to test an alternator for free.
The plug should also be easy to find as a pigtail, that is to say new plugs are available that you splice into the existing wiring.

well i got my most recent one off of an early L27, the only difference was that on the L27, it was mounted upside-down from the way it is on the LN3 and it had a different post in the back, but i just bent the old one, tightened it down and away we went.

It was a ground connection for the L27, but was easily rectifiable as i just said.

They used these on quite a few cars, there are HUGE arrays of cars with the 3800.

Also, look for any squeeking, that can be signs of a dry bearing, and then once they are dry, then the ball bearings break and then they make awful cracking sounds.

Mine was basically brand new from the 92 park avenue i got it from. it was replaced 150 miles before the car was junked.