I had a composite spring on the rear of my 72 coupe crack and replaced it with a VBP 300 (315 to be exact) spring. I had it installed with a new set of standard length leaf spring bolts. I had it on the car for about 1 1/2 years now. The center wheel well arch height is about 28 3/4 inches or so in the back and 27" in the front wheels. It doesn't look bad with my 225/70/15 tires although the front looks a little cramped. What should the arch height be front and rear for my car. I can't find the figures in the service manual. I bought 8" springs and have the car at spring shop to be checked out. I am not sure if I lower the rear an inch or so if the front will come up a little. Does anyone with my tires know what their measurements are? Thanks.

put a matched det of front coils springs in frt,note  as car seats it will level off,i also replaced  rear sparing   and then new upper control arms and bottom arm..note  shocks do not change  height  dwa

Most c3 are about the same. But due to the variations in body construction even within a given model year, they vary. Most are about 29 inches, so your front springs are likely weak. When you replace them the rear may also raise due to end to end load factors.

micar - the average wheel well specs I found in the '72 Assembly Manual are as follows:

Upload the image to your Personal File Folder, then post a link here. I've posted dozens of pages for different assy manuals here...

Cool - let's give this a try.

Yes, taller tires will raise the wheel height.  My reference was with the commonly used taller tire.   The chart will be great.