To continue from the previous post where we had a pile of parts removed from a frame:

This yielded many good parts including another spare set of front disc brakes. Most importantly I have the correct front coil springs for the '68 golden XL now, with these I can get the normal ride height back and do a proper alignment.

The heavy duty (large bearing) 9" is in really good shape. The future plan will be to clean, paint and refresh this axle and then just swap the whole thing into the golden XL as that is really worn.

Regarding the question of loss of spring compression, it is possible if they were overloaded or heated they could compress further than they were designed too. If you need to have a replacement spring made, especially for the front (most crucial), this is how I would proceed. Mind you this can be very time intensive and costly.

I have the tables and look up from the MPC on the rear springs handy on the '68 XL so I'll use that as an example.

First thing is try to identify the current springs in the car. In this case someone wanted more of a rake to the back end so the previous owners added the spacers. But since there is no build sheet I could find in the car, I can still see a hint of violet paint. Just one stripe. If the build sheet is available it too will show what colour front and rear springs were installed.

If you do not have any of this information you can look up the best bet of spring installed.

In this case the rear springs are 5560 as shown in the picture below:

and so we can go to the look up table.

The XL fastback is a 63C body, but since we already have the colour stripe there is only one instance for 1968. Now to the spring table.

In this case the stock spring is located and there is some important information from above that can be passed to a custom spring maker. Now this still isn't enough information to make an exact spring, but it's a start to have a set made to see where the car sits. If it's still not where it should be then after installed and settled any offsets and or ride quality (soft or hard) can be sent back to the spring manufacturer for another try on another set. You can see how this might get very expensive.

Like I mentioned the rear springs aren't as crucial as the front springs. The worst thing that happens in playing with the rear ride height is changing the caster offset (not gain) on the front steering.

For the fronts you want the specified suspension travel or distance as mentioned in the service manual. In this case it's a tool but rule of thumb is you want the control arms in the middle of the total allowed up and down travel. This puts the spindle in the least varying (caster, camber, steering) part of the arc travel and the most stable for high speed turns.

If you want to lower a car, you should always, can't stress that enough, use a drop spindle. Never cut or heat a spring.

On spring selections there are heavy duty packages (towing/handling) and soft riding (luxury) spring rates. I personally like big cars to ride smoothly and I don't see the appeal of turning a big car into feeling like you're riding a cheap go-kart. But to each their own.