I've had both, much prefer a good LS over the powertrax type locker, seen bad things happen offraod with those type lockers, but that could also be that a 35" tire was small,and those lockers might not have liked the load, may be complety different in a car tahn in a truck, but that is just my experience.
Air lockers are cool. I dont think they make them for the 8" though. Not even sure they make them for 9" rears...
Do you need gears if so You can order a decent pumpkin from MAE racing. I think I paid 550.00 or so about 5 years ago. Gears/posi unit/ new bearings and seals. If you need just a posi/locker unit. I would go with a locker too. I am on my third clutch type unit in 10 years.
I had a welded spider rear back in high school. It never broke, but I would never tell anyone to ever do it. As for spools on the street, I have one in my 79 mustang that has about 550hp. I never had any problems with it, but with a novice driver it would get out of hand easy. I`m not argueing with anyone. These are just my experiences.