I agree, there is some issue with the car cutting out.
I did an a/c upgrade and just found I could not start the car after shutting it down because it drained the battery down while running instead of charging.

What I did to fix it was go to the square back alt for an 89 m-body. A newyorker or dippy, but not the cop car alt.
These put out around 74-78 amps and was enough to keep the battery charged with 2 electric fans, and the a/c system going full blast.

For the 318, you need the longer swing arm. I got the 10 dollar gm chrome swing arm that they sell in every parts store.
You need spacers to get the arm out far enough. I got some from the a/c system I put in, but I saw the other day that lowes has them in those drawers in the hardware section.

Then you hook up the single field and ground the other one. It doesn't matter which one you use and which one you ground.