This is what a KR should look like.
http://www.symbolicmotors.com/vehicledetail.php?id=228
http://www.sweetchariots.com/sale3.php
I would expect a convertible KR to sell for between $200,000 and $300,000.
This year at Scotsdail:
1968 SHELBY GT500 FASTBACK sold for $192,500
1968 SHELBY GT500 CONVERTIBLE sold for $313,500
1968 SHELBY GT500 KR FASTBACK sold for $181,500
1968 SHELBY GT500 KR FASTBACK sold for $154,000
1968 SHELBY GT500 KR FASTBACK sold for $247,500. This car is reported to be the first KR ever produced.
So basically you're looking at the guts of $200k to get a fastback KR.