you might be able to make the stock Speed trip bracket work with the existing tabs on the headstock - the TBird frame has 2 substantial tabs with captive nuts which were used on other (faired) T3 bikes such as the Sprint and Daytona. One of the biggest problems you will have is what to do with the bunch of wiring and conectors which currently lives inside the headlamp shell. I dont know if you could fit it into the S3 units in the same way.
I got to ride a bit today and took a good look. Two of the stock lights might be too big, so I'm gonna look into smaller diameter fixtures...I still think the dual headlights would look good, just need smaller cans/bulbs. I'm think that the suggestion for moving the connections to under the tank might be worth looking into.