Since you're in Boston, you need to find a good body shop who can do that stuff too. A few of the guys who did the rear arches chose not to use OEM 1M rear fenders and had stock fenders modified to keep costs down. Although that's a good route to go, I personally wouldn't trust any Boston body shop to do those type of rear fender flare mods. I know the guys at DTM/M1Autobody in LA from way back and there is no one around here in Boston I've seen that can do a similar job. So for me, I would factor in OEM rears fenders.
