Yep, every single 60* V6 in that engine family is 1-2-3-4-5-6. The Buick V6 is not part of that engine family, and AFAIK only had 3.0, 3.3 and 3.8L displacements, no 3.1L "Buick" engine.

And yes, to verify as well, 1,3,5 on the passenger side, 2,4,6 on driver side.

If the engine doesn't run with that firing order, with the correct connections on the dizzy cap, then you have some seriously wrong.

Make sure that the post you have #1 connected to is indeed #1, and also make sure you are going around the dizzy in the correct direction. I don't recall what that direction is off hand, because all but one of my 660s have been DIS for about the last 15 or so years. lol