All you need to do after you rebarrel it, is get a verifier to say "yup that sure is an 18.6" barrel on a semi auto centerfire thus not-restricted". There is probably already a FRT entry with a non-restricted evo 3, especially if Reliable gun is selling one openly
Quite frankly its pretty common to have people rebarrel firearms to different lengths to make them non-restricted, the M1 carbine springs to mind as a common one having an 18" barrel, with citadel selling a 18.6" unfinished barrel to replace it with.