Dave,
Yes, I think the Ken Miles seat is very good, aluminum shell. They will fit the JBL if you rotate the seat about 15-20 degrees (which is where it feels balanced). I had a moch up using a fiberglass shell and it did fit at the widest width / thigh support with minimal trimming. The Miles aluminum shell was not availble when I made my Kirkey's or I may have used them. These seats are very comfortable when rotated to your liking and and balance. Also, they can be mounted very low in the car. I think they are worth the price at $695 and would be a good seat to recommend after fit check to the JBL. Also have to say this seat looks very cool in the JBL.
http://clubcobra.com/forums/showthre...ken+miles+seat
Fatory Five makes a good looking vintage seat for $500 but the Miles seat is superior in support and construction.
http://parts.factoryfive.com/newcata...intagerace.htm
Talk soon, John