I'm in the process of changing the rear springs in my 67 Grande. It has the JF code springs, they are original and seem to have sagged quite a bit. They really drop with a full tank of gas and anything of weight in the trunk. I'd somthing more HD. I've made up a small chart of what I could gather from the net and the MPC's. Will add to it as I find out more.

         
So I tried a used pair of what were said to be 68 F41 springs. They were way to stiff, no travel at all. Taking a close look at the chart suggests these unknown springs are likely variable rate wagon springs like the CC607's. Far to stiff for any sedan or coupe. I take it they were someone's trial gone wrong. These spring are in bold on the chart. 

CC607, Stock JF.

So I went to Carquest hoping to find the HD 1969 spec base sedan 6431's available. They are, $100 a pair. Should fit the HD bill without being too stiff, so I'll try them and report back.

Anyone intersted in these wagon CC607's?

Cheers, Mark