Dave,
There is no possible way to tell what amperage output your generator is just by looking at the outside of it. This factor is determined by the guage of wire and number of turns of wire in the armature and the field coils alike. If the tag were in place then I could look up all the specs on that particular unit and tell you everything about it. Now, with all this being said, if you will send me a picture I can ID the generator by looking at the end plates, the generator case and the pulley and I can tell you what you probably have and about what amperage unit it is. I can determine if its a Caddy generator which would be a higher amp unit or a standard Chevy unit which would be lower output etc. If you want to do this you can send pics to [email protected]
Thanks
Ken