It has to be AC-ready! One way to tell is find the drain line. It ought to be inside a wheel well--you'll just see the end of a semi-hard black plastic tube about the diameter of your finger. I've seen a post somewhere that said the 115V line is also installed and capped at the pre-planned AC location, inside the roof.
I think you have two big problems. First, unless someone knows exactly where the AC was to be located, you'll have to guess. Second, since you've never had AC, you don't have the "plate" installed that was designed to provide a flat spot and to carry the load. The modern gaskets for ACs are pretty thick, like 1-1/2", so the flat spot may not be that big a deal.
Even with the plate installed, I found the structure to be woefully short on support. You can remedy this by installing wood spacers between the inner and out skins around the perimeter of the 14" square hole needed to install an AC or a vent. Once they are secured, you'll be amazed at the monocoque strength of that area--you can do a pullup (remember those?) without deflecting the skins.
see my AC replacement at http://www.airforums.com/forum...tos-20568.html
The old plate is clearly visible. It provided not only the mechanical interface for the AC, but also was tied in to the cover. Modern units incorporate the cover with the unit itself, so those outer rails are not needed. I cut most of them off as best I could and bent the remaining ones down.
You can see I removed the flimsy sheet metal spacers that really only kept the insulation and wires from getting in the way--they didn't provide much strength. BTW, after you cut the access hole, if you can't find the pre-installed 115V line, you will find all the 115V lines going to the receptacles running along the ceiling and just offset about 9" to one side (the 12VDC wires are offset on the other side). You ought to be able to tap into them easily.