Proper Ampage for Alternator

So I had my charging system tested the other day and saw the alt was only putting out around 103-106 amps, at the time I thought that was ok b/c I was somewhat sure it was only a 106 amp alt. Well I became curious and looked at the build sheet tonight and found its a 124 amp alt.

#1. How accurate are the those test that check the alts. amps.
#2. If they are accurate is it ok that it is only putting out only 103 amps.
#3. Could this possibly be tied to something else like a bad spark plug?

TIA
Dave

#1....Probably not that accurate
#2....100 amps will do fine in a normal vehicle with out a winch or major sound system
#3....I will have no bearing on a spark plug.

Along these same lines does anyone know what the maximum the altenator can be wired to put out? I asked b/c the local auto electrical shop will rebuild an altenator for a higher output @ $1 an amp overall. In other words if you want a 175 amp altenator they will rebuild yours so it will produce 175 amps for a cost of $175. So how big should I go? BTW I do have a winch.

I just got an old one rebuilt to 160 amps and it only cost about $100.

Jess said:

I just got an old one rebuilt to 160 amps and it only cost about $100.

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Is that the maximum you can go on a stock altenator?
My guy was assuming mine would be in need of a complete rebuild after 240K miles. Me too!!!

old_man said:

#1....Probably not that accurate
#2....100 amps will do fine in a normal vehicle with out a winch or major sound system

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I kind of figured, just wanted someone else to say that for a little assurance. Thanks guys for your help.