Nice bike btw

....and welcome to the Savage forums!
You are correct in assuming that very few changes have been made to the bike over the years. Starting in 2005, the bike was re-named the S40 Boulevard and the handlebars changed (along with the seat, fender, and a few small items).
So far as I know (and I'm NO expert by any means), virtually no changes were made to the bike from '86 to 2004. All of the mechanical parts should be interchangeable. Electrical?.....not sure.
You will find that this community has more knowledge about the Savage than you can find anywhere else in the world. If you need info, ask. Just a hint...the "search" function is set to "2 weeks" by default. Searching without changing that will yield you nada. Change the search time frame to at least 6 months.