I would think finding a pair of leaf springs and shipping then across the pond would be cost prohibitive.
Air springs work, but the body mount piece of sheet metal (crossmember), doesn’t like the extra stress of air shocks. I have seen that rear upper shock mount fail on several cars that had air shocks installed. Where it fails is almost always where the body mount connects to the frame rails – and generally is not an easy fix.
The red circles are the (only) places the body mount attaches to frame rails (or anything, for that matter). The blue line/blue arrow is where the upper shock bolts are at.
If a person was top reinforce that upper mount, I would find a way to attach the mount to the trunk pan on top as well as weld in struts to the lower half of that mount. What happens is that part starts to twist in place until it separates from the frame rails.
Now, I have seen it happen a few times and only with cars with air shocks. I’ve not seen it happen with normal shocks. I have also seen several cars with air shocks without troubles.
If I was dead-set on using air shocks, I would reinforce that mount – or also for extreme usage (all out road racing).
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What I would do is inspect the area, if OK, then leave it alone. Then take your original 4-leaf leaf springs and get them re-arched and additional leaf installed at same time, at a spring shop.
That way you are set and ride height has been increased to whatever you desire.
Removing the Iso-clamp will also raise the car up by about ½ inch (13 mm) or so.
The first picture is from ’72 parts book, I think.
The second pic is from ’82 parts book.
The second pic, item # 22 is the rubber biscuits that insulate the road and makes the car fleet soft. Also item # 21 is the weak link. If it breaks, then that corner of car is dragging the ground.
Firm Feel makes a delete kit that reuses some existing hardware (reuse old shock absorbers).
I recommend finding some ’60-72 shock plates (and new U-bolts). Some people are making them new. They will require different shocks because of the rear attachment is different. The shock length is the same. Just look for say ’70 B-body rear shocks and they will fit fine.
Aftermarket New
Used
If using the older shock plates, you will need to have “normal bolts” re-installed (when getting old springs re-ached at spring shop) instead of the Iso-clamp wide version (they will reuse old bolt – which won’t work with older shock plates).
To recap:
In my opinion, it is worth the effort to get rid of the Iso-clamp system using either older shock plates or using one of the aftermarket kits. You may need new shocks as well and going through the effort of springs and such, it makes sense.
I would prefer you not to use air shocks – but I can’t stop you. Raising the rear ride height via springs make a lot more logical sense and afterwards – you might not even need air shocks. If still considering air shocks, look into reinforcement of the upper shock plate (crossmember).
BudW