The beauty of the America is that it is perhaps the most impressive "stock" bike out there - and I may be biased - to the point that you really don't have to do anything to it if you don't want. That's the difference between style and fashion - the TBA is simply stylish. Period.
All I have added since 2003 are EasyBrackets. Other than that, it's still turning heads and I can't leave it for 10 minutes before someone starts checking it out.
Enjoy it as it is or tinker to your heart's content. The good news is that you treasured Triumph will remain a thing of beauty and a joy forever.
Siggy