I was in the same position as the OP at a weight of about 375. I contacted several local LBS's and all offered to build me a wheel but when I tried to find references of people who had gotten a wheel from these shops.....NADA. I have no idea if a given shop builds 10 wheels a week or 10 wheels a year. Also, the local prices were within $20 of at least one guy online who does nothing but build wheels (over 6000 at last count). I decided that my needs were severe enough to warrant going to a specialist and I picked Rich Lesnik of Rivendell Bicycle Works. I told him my weight, the type of riding I do, the drop-out spacing of my bike, the size rim, the type of brakes I use and the cassette I'm using. He did the rest and I ended up with no-name touring hubs that he likes, Velocity Dyad 40 spoke rims laced 4x with DTSwiss spokes with brass nipples. He warranties his wheels for the life of the rim. Total cost was a little over $400 (for two wheels) plus shipping.

Rich is the only builder I have personal experience with but I've heard equally good things about Peter White, another dedicated wheel builder. Both guys serve the same crowd, namely commuters, tourers and off-roaders (hard packed earth rather than technical trails), folks who use and abuse their bikes and who have to have wheels that hold up.