This is the cheapest path, but you'll need some precision to keep it flat if you are not good with body work. My top and bottoms didn't align well and had to form an extension of this shape. But, I restored a vette and got better at body work than I every really wanted. I am sure Sam (Sabre) could make you up the spacer you need or you could make your own from flat stock, cut to shape and use the spinner bukheads as drill templates. You could place it between the spacer and the inner spinner bulkhead.
My clearance is under 1/4" and no noticeable interference over 70 hours. In my research, I thought most guys were going between 1/8-1/4"
Larry