What are you building...bone stock?
One noticeable difference is sidestand mount, further back on Fmodel, maybe slight difference in rake,, sidecover. And pipe mounts will be a bit different.
But , it may not even really matter that much to you.
Around here altered number can cause a lot of grief, but you may get your bike back a year later, wont be any paint on the neck..
That bondo on the numbers idea, sounds like the guy is on crack....