"the small plastic box with a brown wire coming out of it on the back of the alternator?"
I think that part with the single brown wire is some kind of radio suppression device. Not sure if it is essential. B.C.?
--
1980 245 Canadian B21A with SU carb and M46 trans

The external regulator is a small box mounted just behind the right headlight. There is a 3-wire harness from the regulator to the back of the alternator.

If your 1982 doesn't have this set up, it's an internal regulator alternator.

The alternator needs three wires to do its job.

(1) The ground wire. It's a black fatter wire, connected under the rear bolt holding the mount onto the block and the frame of the alternator - often under a frame nut on the alternator back. Sometimes there is a spade lug on the back of the alternator that's held there being under a frame nut.

(2) The charge wire. This is a really fat red wire, connected to the alternator on a big stud with a nut and washer. Often there is a plastic cover that clips onto the washer and covers the nut connection. this wire is hot all the time, and carries the heavy current to the battery via the starter.

(3) The exciter wire. This is a thin red wire with a female spade lug connection to an insulated male spade lug on the back of the alternator.

All three wires must be connected. No more, no less.

If you can connect these to your alternator, it should work OK.

BUT - the 1986 has the B230F engine which uses a different type of crankshaft pulley than the older model. The belt alignment may not line up right. Be sure to check.

And - The alternator lengths may be different. If so, swap the bracket, too.

Good Luck,

Bob

:>)