Charging wiring question

IF I recall, the Classic got alternators before it was standard in American - I'm pulling from a non-coffee memory. Guess I could go check my charts LOL

In any case, do not use a generator regulator!

What is the MODEL of the alternator? Should have a tag with MODEL number.

Motorola regulators for AMC only had FOUR wires, unless it's an R2-1 which was made to replace the TVR for AMC. The R2-1 has 5 wires, 2 of them yellow that go to the fender mounted charging system resistor, a black, green and red. 
All others have just FOUR wires - orange, yellow, green and black. There are no letters or + or - signs on the Motorola regulator. 

Again, unless someone changed things, a 76 engine has a Delco alternator (unless it's Jeep - could be Motorcraft, and some used Bosch) 

But again, don't even try to use the original generator metal box regulator on a Motorola alternator. 

Jeep - that's fine and yes, the Motorola alternator will make it pretty easy in the end. 
REMAN - should have guessed that as they use totally different numbering than stock or new parts. 
Yeah, the literally RIP the tags off and literally rip the alternators apart when doing a reman on them. 
Knowing the YEAR the alternator is aimed at will help a ton. 
You need the 8RH2003 or similar regulator. You will HAVE to use a 71 or later style regulator, not the earlier R2xxx series as those are meant only for alternators with the red isolation diode on the back. 
Yours will not have that being for a 71 or later AMC/Jeep vehicle. 
So you need the FAR FAR easier to find 8RH series or similar. Those are everywhere - eBay, I likely even have some. 

Most of this will be easy - the green wire from the CORRECT regulator goes directly to the ALTERNATOR field - the brush connection.
The black wire of the correct regulator goes to a GROUND spade on the alternator next to the green field wire.
The yellow from the correct regulator goes to the ignition feed

The orange from the correct regulator goes to the REG connection on the alternator AND to the dash ALT light. 

If your alternator does NOT have the two condensers, IGNORE them in this photo! That was an AMC thing as techs were blowing charging systems while disconnecting diagnostic equipment with the engine running. 
So ignore those. 
IF your alternator does NOT have the connection for the electric choke, IGNORE THAT, too.

Yours may look like this - same thing but with no choke output and no condensers on it.

Orange spade on upper left, battery lower left, green to insulated spade for brushes at top, black to the spade that is PART OF the plate over the brushes. 

The wire from alternator to the battery (typically they use the starter solenoid as the junction block to tie the battery to all of the wiring that needs battery power) should have a fusible link wire. In other words, the wire coming from the alternator goes up toward the starter solenoid (I said "up" assuming the Ford style fender mounted solenoid/relay) and it turns into a fusible link - there's a sort of black molded part where the wire connects to the fusible link. That link is designed to burn out, melt away inside in the event of a "short", saving the rest of the wiring from being fried. 
So it's smart to not just run a home-run wire from alternator up to the battery connection but use something like a fusible link in line with that connection - and yes, the auto parts stores often carry them - or can get them. I bet you can even order them from Amazon, maybe some of the AMC vendors listed in our vendor section have them since AMC used them in everything for decades. 

Since you are going it from scratch, I'd shoot for a 10 gauge minimum - but if you may do some changing later, go 8 gauge. That way if you decide to change to a system putting out over 65 amps you are ready. 

8 may be overkill for, say, a 55 or even 65 amp alternator, but it's best to make it larger now in case you ever make other changes later - like electronic fuel injection with an electric fuel pump, that sort of thing.