I would definitely re-buy my hotair if I had to do it again... but then again, I was in a different position than you were. I bought mine because I needed a car (mine had just been totaled), I wanted it to be a GN, but I didnt have the budget for an 86-87 GN. It was either a hotair GN, or no GN at all, and I got a good deal on an unmolested 85. As has been mentioned, if your ultimate goal is to run low 12's or 11's, youd probably be better off going with an IC car. It doable in a hotair, but will take more money and effort to get there in the long run. If all you're looking for is a clean GN that will run low 13's, then a hotair can do that pretty easily, and will generally cost a bit less than an IC in the same condition.
another thing to consider. While the hotairs cost a bit less nowadays, who knows what prices will be like 15 years from now. When you consider that TOTAL production for hotairs (84 AND 85, GN's AND T's) is somewhere around only 2000 cars (I dont remember where I got this figure from, I seem to remember reading that somewhere, if I'm wrong, someone please correct me) then the hotairs are quite a bit rarer than the IC'd cars (they made like 20,000 of em in 87 alone, if i recall). I have no idea what the prices on these cars will be like in the future, but if you look at 30-40 year old cars nowadays, an original, early model, numbers matching, with a low low production will generally get you quite a bit more money than a later model, even if it has the better engine/performance, but had higher production numbers. Like I said, this is all jsut speculation on my part, none of us know where prices will be in the future. Maybe I'm just telling myself this to make myself feel better
Theres also the draw, aside from possible increased value in the future, of having a rarer car. I've been to a few car events with my GN, and even some TR only events, and I've yet to see another hotair in person at any of em. Mines not in GREAT shape (body is a little rough in spots), but I still get a LOT fo attention from the people there, especially the TR guys, since a lot of them havent actually seen a hotair before. Its kinda cool when I pull up next to 5 or 6 GN's at the local cruise, all of em with huge turbos, chrome aplenty under the hood, great paint jobs, etc. and I have people wlaking past them and looking under my hood because I'm the one thats different, or that they havent seen before.
whichever way you choose, bet of luck... and if you DO get it, welcome to the hotair world!!!