Guys;

There is nothing sacred or even special about the IS...it is merely a common electrical point (isolated from the chassis), at which several wires connect together, and which results in the option of having wire where an AMP meter could be conveniently connected. It also somewhat simplifies the wiring modifications when doing the Alt conversion, from Before to After, specific to the original Volvo wiring...I point out that the battery + terminal is NOT the common electrical tie-point on vintage Volvos...with their single fat wire connecting Bat + Term. to the Solenoid at the Starter, this is where the Charging System output (source) and Light and Ignition Switch (loads) were connected.

...I agree that the Alt output could simply be connected to the Bat+ terminal...however, a convenient point at which to place the AMP meter would then no longer be available (reference the "H" diagram in electrical Ramblings tech article)...

...botom line is that if you are experienced and confident enough to know how to wire the system up....you certainly can forgo my instructions, but if you don't have this level of qualification, or simply just want to follow instructions with a proven track record, then do that with confidence.

Hope that helps!