Surely there were more than a few 5sfe powered camrys with aircon? Perhaps it's just a matter of searching through some wreckers until you can find the aircon system out of one.
My parents had a '94 widebody V6 Vienta/holden apollo - a great motor but blew the headgasket(s) at 140,000kms. $3500 later it was as good as new (new VRS kit, new cam bearings, heads straightened) and had over 350,000kms on it when sold . Still performed well with only the slightest puff of smoke on startup but was starting to get a bit rattly.
IMHO it's prob not worth doing either a V6 or a 3SGTE conversion. If you want a V6, it'll be cheaper in the long run to sell your car and buy a V6 - and the same goes for a 3SGTE - ST165 GT-4 Celicas can be had for less than $6K these days.