Offcenter stg2 with AC

I can tell you from my own experience, if you have an Off Center S2 Buick Motorsports block, the factory "86/"87 LC2 accessory bracket and belt tensioner will bolt right up. I was able to bolt up all of my factory accessories on my 1st car, when I dropped in my 276 CI Stage 2 Off Center long block with no issues and nothing special needed. Everything worked. 3 pics attached.
Have you tried reusing the factory drivers side cast aluminum accessory bracket?

I know years ago Champion made an alternator relocation bracket and RJC has some options as well.
Hope this helps.

However, I will add this tidbit.
If you plan on using Stage 2 heads.... my memory tells me there's no drilled and tapped bolt holes for the drivers side accessory bracket to bolt to, nor on the passengers side where turbo heat shield bracket would bolt to. I'm also not sure if there's enough meat in the S2 casting to drill and tap them without hitting the coolant passages in the head. All of the standard style heads, GN1, TA Performance, have these holes drilled and tapped.