If You mean keep the true duels and just go to 3.5's yes just make sure the 3.5's are for true duals like a few have said slipons are a bit smaller inlet than the true duals which are 2".I think just slipons for a stock and aftermarket headpipes are 1 7/8.I got fuelmoto 2-1-2 headpipe that works well use your stock shields,But doh't get Me wrong the last couple weeks I've been thinkin bought true duals maybe a little better sound but performance wise a might be a bit better with a 2-1-2 system but don't think Your butt would notice it just a Dyno sheet you'd see the difference.

 

You could always just change the baffles like most of us would.