Attached is a pic of the pre-69 tail pipes. Interestingly, they were retrofied to the "official" 69 Pace Car, Serial #1 & #2 used to pace the race. These tail pipes were used to provide clearance for the caution flag brackets. These pics were taken last year at Indy for the 2006 Indy Pace Car Reunion celebration during the 2nd time trials weekend.
The added support spring was added to keep the rear of car from sagging when the winner, Mario Andretti, and people road in (and on) the car during the victory lap.