Just remember that the 105 amp rating is a max rating or an advertised rating if you will.
And sometimes they play games with the ratings.
And does the one you have in your hands really meet the specs?
Only a good alternator shop could test that.
The important aspect is how much current will it produce at what RPM.
The output curve.
And of course - how much equipment you are running in the car at that time.
Higher amp stereo?; Heater or A/C?; higher output headlamps?; bigger FP?; Dual fans? etc etc
A temporary digital ammeter gauge (remember those? - cheap in the analog style) could be used - in fact - even a rigged up industrial hand held DVM style meter for basic monitoring would work to get a handle on max current draw.
But trying to simulate all loads on and at max worst case is tricky at best.
That's why there is that excess or slop factor built into the design using the stock CS144 120 amp unit- or the upgraded CS144 140 amp model
The big big killer is IF you exceed current capacity of the alternator, the rectifier generally will start to fold back the voltage - a big no no with our stuff, since we go to such great lengths to increase voltage at key components.
The other phenomena experienced is when approaching max load - not even at max load - there is a voltage output "sag"
Again - bad.
I respect Steve's write up here:
http://www.vortexbuicks-etc.com/alternatorselection.htm
