Front Fork Shock

I had quite a bit of pitting on my original air valve shock tubes so I decided to pick up a cheap spare without air valves and swap out the tubes while I was redoing seals.

Now I've taken them apart and they're quite different inside!

The Air assist shocks have a smaller spring with quite a large spacer...
The Replacement non-assist shocks have a long spring and no spacer...

My question now is, what do I put back in when I put them back together?

Is there really any value in the air assist or is it just marketing? Would it be better to put the longer springs in without spacers? (Why do the air assist have shorter springs in the first place?)

Finally I also have the option of removing the 25+ year old springs and replacing them with progressive springs...

So basically I have 6 options:

Air assist with short springs
Air assist with long springs, no spacers
Air assist with progressive springs and custom spacers
No-air with short springs
No-air with long springs, no spacers
No-air with progressive springs and custom spacers

Has anyone been is this predicament or know what the best course of action is? I can take pictures of the difference in sizes if anyone is interested.

 

Those will be your best options. 30-year old original springs are worn out. Progressively-wound springs are a great improvement, even over brand-new "dual-rate" springs as were originally used on these bikes.