Hubcap,
Were I sending it to someone for rechambering my first chioce would be SSK I've had a few barrels that were rechambered by them, a 309JDJ, a 358JDJ and a 444Marlin and all were great, no tool marks/scuffs on the outside of the barrel like I've had from some of the other smiths.
While I've never had anything done by David White all that I've heard about him has been positive so you may want to try him if you dont want to go to SSK.
Come to think of it, I own/have owned full custom and or rechambered barrels from Bower, Bellm, Bullberry, Fox Ridge, Reeder, SSK and Dave VanHorn and Virgin Valley and so far the only ones that I haven't had any problems with have been Fox Ridge, SSK and VanHorn.
If you want to do it yourself check out
www.4reamers.com for a rental.
Mark