Nominal 1000 lbs was the usual "limit" for those. Anything over 500lbs in the back is going to be an issue. Towing 800lbs would be no problem.

As for a hitch, find someone who knows what they are doing, as you'll basically be bolting it into sheet metal. And then there is that darn gas tank in the way....

I towed one of these (with not a lot in it) with a '65 Mustang and a hitch bolted into the floor of the trunk in front of and behind the gas tank.

http://www.uhaul.com/Reservations/Eq....aspx?model=rv

I've probably been closer to death than that trip, but not much... Although it went without a problem I must say.

As for air shocks--no. Get good shocks that control the car.

Overloads? No. Size up how the rear suspension works. Smooth ride? Too smooth? Does it really sink with 400 lbs in there? (Invite several skinny or a couple fat friends over to stand in the back) What I did with that Mustang was to add a leaf. The old springs were flat at rest, and the new leaf gave me about 1.5-2 inches in the back, and put some arch in the springs. It rode much better after that, since it wasn't hitting the bump stops all the time.

What axle to do you have? Probably an 8" with a 3.25 ratio. You should consider an AOD as you'll be running a lot of revs on the freeway if you're geared that way.