if you keep the wheel size the same and get a springer the same (or similar) length as the stock forks then rake/trail should be close enough to stock to not screw up the handling.
HD necks and bearings are different from the Triumph's, but you could possibly press your stem out of your bottom tree and into a springer.
When I did my front end swap I had a machinist press out the stem from my stock trees and into the other trees I used.
