There are lots of pictures on the net, that show the rear bulkheads, the weldment to hold the tail spring, and the aluminum bar stock that the horizontal stabilizer bolts too. For the standard 6A's the bar stock (dimensions somewhere around 1/4"*1 3/4" or 2") was vertically straight on both sides. For the tail wheel, it's a V-shape, with the bottom of the V bolted to the tail spring weldment. As I remember, some QBs were already produced this way. But I'm not sure.
For the tailwheel, two rear bulkheads are riveted together back to back for extra strenght. If the V-shape bars are straight, then that bulkhead needs to be changed to. This requires the rear deck to be un-rivited. Nothing major.
Front landing gear & engine mount is changed. Get rid of the tri-pod gear mounts in front of the spar to for weight. Leave them, if you ever decide to change to a nose wheel.
Sometimes, the bottom of the rudder, might need little fiberglass rework, if it hits the tail spring.
Off hand, it seems like the replacement parts were in the $1400-$1600 range. I haven't checked current pricing.