Yet another Carbed ls alternator Question

[lt155ruck]

Sorry in advance to everyone that has ever read or replied to the thousands of these questions. I have spent Hours reading and now am more clueless than before I started reading.... The motor is in and it seems all the fiddly Bs is taking FOREVER.

This is the scenario. 1972 2wd Blazer with a vvt deleted ly6 6.0 that is CARBed and a 700r4. I'm using a truck alternator with the 4pins. From what I THINK i understand "S" and "P" will remain unconnected. "I/F" will go directly to a switched 12V source and "L" will go to either an idiot light or a 470 ohm resistor. The other side of the bulb/resistor will go to a switched 12V source.
my questions are

1. Can i connect the brown wire from the original Blazer harness that was originally going to alternator to the ''L" ? will this illuminate the alt/gen light in the dash? I've read conflicting posts that the light stays lit all the time? can anyone confirm this? or dispute

2 What is everyone using as a switched 12v source to power both the I/f and L terminals? Is there something I can tie into under hood? maybe the original voltage regulator?

3 what happens to the other wire from the stock Blazer harness that goes to the original alt? is that a switched 12v source that i can tie into.

Again I'm sorry for making you read yet another question on this but i really need clarification specifically for my 72