I have a Salem Kroger converted Sportsmobile van. In my experience it's often tough to find folks who'll work on custom vans, so here are two of my favorites in the Bay Area:
4Wheel Parts:
http://www.4wheelparts.com/stores/Store-Info.aspx?sNo=12 This is the Oakland store.
They did tremendous work on my front steering, ball joints and brakes. All very tricky.
Any Seven Off-Road: In San Leandro.
http://www.any7offroad.com
They are offroad fabricators; more in the Pirate4x4 mold than the Expo Portal mode, but in my mind that's a good thing. They fab'd a front winch mount that went inside my stock Ford bumper; very sweet. They also did a bunch of fab work for me on a Tracker I owned. They've got a good sense of design too, so if you have an idea they'll make it better.
VTE Warehouse:
http://www.vtewarehouse.com
These folks make busbars, terminals, battery terminal covers, fuse setups, etc. A great source for electrical components. I used their stuff to fuse and wire up inverters, winches, etc. I got tired of getting ripped out at marine supply places for this stuff; these guys are very efficient and WAY cheaper.
Parts:
http://www.pathfinder-vans.com/html/salem_kroger.html
These folks have super hard to find parts for Salem Kroger conversions and Pathfinder conversions. Not a huge selection, but some stuff.
Whitefeather conversions:
http://whitefeather4x4conversions.com
Craig, formerly of Salem Kroger, is here. They do Sprinters now, but I did get some Salem Kroger stuff from them. Very nice folks.
Rob