I had Clarks do some work a while back (years). It took forever (months and months to clean up a Ruger revolver trigger and chamfer the cylinder), but the work was great. Too much internal politics around that place for me, though, and I stopped frequenting their shop or store (it shut down?).
Willis Arms is also someone I would check out, he can either do it and will tell you, or he can't and will tell you. I've had great luck dealing with him and he has a very nice little shop.
Willis Arms Repair Inc.
James Willis, Gunsmith/FFL
1607 Hwy 527
ElmGrove, LA. 71051
(318) 742-7432
Hours: 9am - 6pm Mon - Fri
sales@willisarms.com
+1 for James Willis. He is very knowledgeable and there isn't a project I wouldn't trust him with. He is also very reasonable price wise.