Maybe I'm not being basic enough. There is no true "tensioner", the components on a v-belt drive system are moved in and out to allow the belts to be removed and the belt tightened after replacement. The A/C compressor has a seperate belt, i believe it just runs off of the crank pulley, I may be wrong. I believe the alternator is adjustable, it usually runs off of both the crank pulley and the fan/waterpump pulley, but the alternator is the adjustment point just like the A/C compressor is. The power steering pump is also adjustable for removal/replacement/tension of the belt.
Now that I think about it, on the gray market car I worked on, there was an intermediate pulley, I believe for the A/C, the pivot bolt was loosened, which allowed the adjustment of the intermediate pulley. The one I worked on was about an 83 or so, had the M110 engine, dual o'head cam inline 6.