swapping from 37 amp to 55 amp, direct swap?

dogbone, I think the original intent was to stay with  Motorola. Rockauto might list a Delco 10si but it will unlikely be a bolt on without changes, including to the regulator. IMO it is more obsolete than the Motorola, and for sure doesn't charge much at idle. If you are changing out completely then go with something much newer.

Back to Billd's explanation of why a higher amp alternator is required for A/C. Back when I had my 73 with A/C. I have lived in San Jose, CA. The stop and go traffic and heat required A/C. Thankfully, it was not like Georgia, with high humidity and heat up into the 80s at midnight, in late April. Reasons being lights, stereo, A/C, and stop and go traffic... you guessed it. The alternator would probably give up the ghost into to anything but a high amperage version.

Now back to what I was about to explain further. I had requested a replacement high current alternator and probably got a 37 amp. Thus after a year, again needed another alternator. Again I requested a high current alternator as I told them I had A/C. Again the same old same old happens after a year. This time I never got around to find out if it was a high current alternator or not, as I made a change out of engine, and pulled my A/C compressor. So without A/C how is one to tell any better? Well for that experience for me, the question is mute. Just some info about why high current does not mean you are going to use more current in general. It is to have more current capability at idle and below 2000 RPM.

Most alternators don't produce enough current below 2000 RPM for all the accessories, unless over driven like police, and heavy duty options.

S Curry wrote: I guess I'm curious as to how much running the AC will draw for current. I'll get out my Fluke with a clamp and find out. I would believe 2 amps on the comp. clutch, but I'm thinking the fan at high speed is more than 2 amps. I'll find out.

The Sanden specs are 3.6 - 4.2  and that's SANDEN.
Some others draw more. 
I've done some repair on cars where the switches and other parts were damaged by the draw. Two is very under-estimating it. 

If you watch a volt meter when the AC kicks in you can see a response that indicates it's more than a paltry two amps. 
The resistance of the coil on SOME units is two to five ohms - that's not offering a lot of resistance. 

304dude - it's the problem with those bloody reman units. 
I have had so many apart over the years I swear I will never ever ever buy a reman alternator (or carburetor etc. )
Those reman are will-fit, like I said. I've seen them built and I have gone through hundreds of alternators over the years and have too many to count in my shop (unless I get really bored some night)
Heck, I'm doing a dozen roughly (ugh, I'd have to look at the list again) just for Ross ..............
I've seen a few alternators, and many many reman, and some people "swear" came from AMC and I know they may have been removed from an AMC but AMC never put them there originally....
I can tell by looking what's right, wrong, size and so on. 
In some cases I can tell you the year and if it came from a six of a V8 by just looking even with no tag. 
Yes I've done and do that many. 
Reman are parts from many pulled to put something together. They don't always match year or output and the frames aren't always even correct. 
I don't even like getting REMAN units as cores - and I've seen some supposedly rebuilt by others that make me shake my head and worry for the owner of the car.
When you buy from a parts store you are tossing dice on reman Yeah, they guarantee things but I guess that's up to the car owner as to what they want to do........ change what they are given or get the correct item, as far as remanufactured alternators. 
Remember, these employees don't always have any training, either. Some are darned good, others wouldn't recognize an alternator if it was sitting in front of them with a sign on it. And higher amp - they go by the BOOK. If the book says YOUR car should have xyz that is what you get. They can't think outside of the book (HAHAHA)  ;-)

vinny wrote: dogbone, I think the original intent was to stay with  Motorola. Rockauto might list a Delco 10si but it will unlikely be a bolt on without changes, including to the regulator. IMO it is more obsolete than the Motorola, and for sure doesn't charge much at idle. If you are changing out completely then go with something much newer.

I have to agree with ya.......

10si isn't worth the swap, IMO. Not as good at idle, takes more power, etc. Little gain other than no external regulator on the fender. 

Motorola made alternators for MANY makes and models, not just AMC. In fact I have a brand new Motorola on my shelf for Toyota, and I've worked on them for VW, and some higher-end European cars. 

AMC did use Delco on later models - Spirit, Eagle, etc. - it was the 10si and I have parts on hand for them, a few cores, as well. I have a NOS Bosch for AMC as well sitting somewhere. 

I took it out tonight just to see how the new A/C was going to perform with air running through the condenser. Good news is it blows 45 degree air and seems to work great. Bad news the original alternator is not going to keep up. Was running in a worst case scenario, lights on hi beam, blower on full blast, A/C on and the outside temp about 80. Volt meter reading about 11 volts and maybe on the low side of that.