Here's a reputable place:
Diesel Specialties of Omaha Inc
13325 B St
Omaha, NE 68144-3611
Phone: (402) 330-0580
I had mine installed by Woodhouse, and they created a mess - I would most definitely <b>not</b> recommend them for that kind of stuff (would recommend them if you're looking to buy a new one; they're grat to <em>deal</em> with, literally!).
The A-pillar mount wasn't put on right, and around the trany temp probe I hade a leak from h*ll. They then "fixed" it and in the process killed my pan. They then gave me a new pan, drilled a hole, and put in a way-too-big pass-through for the probe, so then it read about 20*F too low (only the very tip was in contact with the fluid). I finally had to buy a Mag-Hytec pan to get this fixed...
Even though it was messy, they were rather nice about it, putting in a lot of hours (to fix their mess-up) without charging me for it...
If I had to do it over again, I'd go to Diesel Specialties!
PM me if you want to chat more...
Alain, Mondamin (IA).