[CompClassics]

The spacer you want to use should be of a one piece design that fits the same surface area that your present spring fits on, the reason for this is clamping force by the securing bolts in relationship to the spring movement. I have photos somewhere of the lowering block that was used on CSX2323 that I took when working on it years ago. The owner at the time Jamie Mazzotta liked the car lowered so he had the blocks made out of one piece of billet aluminum. The design was pretty cool in the fact that he incorporated rails on the edges to help trap the spring from pivoting on its centering pin. The lowering block also had bevels along the length of both bottom edges to clear the tower welds and the block was wide enough to to be trapped by the spring towers front and rear flanges to further stabilize the spring from movement.
That being said, how many miles have you put on your car since completion? These early 7000 Series Cobras has notoriously week leaf springs that would start to sag pretty quickly. Are you still running the stock Shelby springs with the camber adjusting system at the ends of each spring, front and back? There is a reason I ask and I will await your follow up on my questions.
The photos that 1795 posted are functional but only 1/2 way there compared to what I am describing above, especially if you plan to track the car.