Hey, Marine!
Good to hear from you, and hoping all's well in Okinawa.

Responding to your question about a T-Header on a Dyna would be only guessing on my part, as the FXR is an EVO motor, and the current Twin Cam such as you would be getting on a later Dyna is a different beast altogether. That being said, there are certain features of that header that you can expect on any motor, including your Sporty. You are already well aware of the sound output of a T-Header - awesome, whether just idling, in cruise mode, or at full throttle! On a 96" BT the sound will be a little deeper and maybe a little louder than your 1200, and there's a little extra vibration you might feel while on the road or even just standing next to it if you're warming it up in the driveway. Running a mild cam and a hi-flo air cleaner I had to make several adjustments to the carb (jets, needle) to maximize the performance of the header; even so, power output seemed a little soft in the lower rpm range. But once you get beyond that point, the T-header will give you all the horsepower your motor is capable of, if you can hang onto the throttle!

On a 96" or bigger motor, that flat spot will not be as noticeable, perhaps not even felt, as there is so much torque down low in the newer BT. But you will still have to mod the EFI (or carb if it's an older Dyna) to get the motor to run decently, especially if you add a performance air cleaner or a cam to go along with the T-Header.

Sorry for the long post, but I wanted to answer your question as best as I possibly could. And btw, just last month I replaced that trusty FXR with an '010 Dyna Fat Bob, and I've been on a new learning curve the last two weeks. Wish you luck finding your dream bike when you get back home. Stay safe. Peace.