There are a number of ways to do this. Air shocks are NOT the way. The top brackets to which the air shocks bolt to are not very strong and essentially you are lifting the car using these brackets - they will fatigue and break over time.
Taller springs from a station wagon will lift the rear up, but not 3-4 inches. You'll get a couple more out of them. Do a search using the Search feature on this site and you will get a number of ideas and spring choices.
The next option to get the car up 3-4 inches is to put a pedestal under the coil springs to which your coil spring will ride on and the pedestal seats on the rear axle where your spring would normally seat. You want something like this: https://www.ebay.com/itm/3-Inch-Pont...4AAOSw4-hZr6Aq
I loaded up a pic of my '68 Lemans with the 3" lift pedestal. You will want to drill a hole in the center of these so you can run a threaded rod down them to attach them more securely to the axle housing mount. I also plan on using some form of attachment to keep the base of the coil spring secured to the top of the pedestal.
But, don't get all googlie eyed just yet. Adding the lift will change the geometry of the rear suspension. Those upper control arms are going to be at a severe angle and almost useless - if they don't simply hit the rear crossmember near the attachment. Wheel hop can already be a problem with the stock ride, but add the lift, you might have more problems on your hand. First, you will have to add a little more extension to your shocks so they work correctly and are not "stretched out" so as to make them worthless. Next, to correct the upper control arm angle, you will need to raise them up at the rear end side. "No Hop" bars can do this and they are sold aftermarket under several names & companies. I fabricated my own to fit the 9" Ford I'm using as no one makes a bolt-on for such an application. Don't forget to use a longer rubber brake hose so the stock one isn't so stretched out all the time.
Then jacking it up will most likely affect your pinion angle and to counter this you may want to consider adjustable upper/lower control arms to get things back in line again.
Now with that all done, you have changed the center of gravity and the way the ass-end is going to shift around - so add a sway bar set-up to counter that situation.
BUT, I'm not done yet. All that weight is now going to be somewhat shifted forward to the front of the car and the stock springs may not have sufficient spring rates and you could find a more "bouncy" front end as well as steering differences - ie under steer or over steer. I went with a rather stiff 1970 Chevelle 454 spring as I also want my car to sit high in the nose to go along with the raised height of the rear. Front brakes may be affected as the weight shifts forward when you hit the brakes - better have disc's and an adjustable proportion valve to get this set-up correctly. Wide rims/big tires will round it all out on my build for a little better traction/handling overall.
Yep, the jacked-up look is from the '70's era and looks cool to me because that's what I grew up with and am modelling my car after - except I am doing it right and doing it safer.