Hey mate, nice find you have there.
Aircon is possible. The units are quite rare but eventually you'll find them. I've fitted half of one so far into my KE55 Hardtop (SL2). I plan to fit another to my panelvan and another to my KE30 sedan.
I too want to put power windows in mine. Let us know how you go, I'm hell keen to see how it turns out.
And as for the tail lights, I'd go the update KE55 hardtop tail lights. I've fitted them to my car.
Feel free to check out my thread. The link is in my sig under Skanky-Loue (SL2)