I just changed out the coils on my 67 RS conv. I pulled the original factory springs out and replaced them with SS-405 ($149/pair) springs from rick's. the result was that the car now sits over 2" lower. The description of the SS-405 springs say that they are built to original factory specs and should maintain original ride hight. When I called Rick's on it they said they have had problems with those and would do the right thing and replace them for free. They are recommending that I use the SS-40's instead. SS-40's are half the price of the SS-405s, but if they work I don't care. Does anyone have any experience witht these? As a side note I am running 135 sized tires. Anything lower than 15.5 inches from center of wheel to lip of fender is too low.

Not sure about Ricks springs, but as a data point my Moog 6308's sit at 15" in the front.

When you pull the coils out, check them for a stamped number near one end. If there is a number, it may be a Moog coil.