For catalogs, LMC has the best, but here are a few more that have catalogs:
http://www.classicparts.com/
http://truckandcarshop.com/
http://www.brotherstrucks.com/
http://www.earlyclassic.com/
For ordering, I try to stick with board vendors (Brother's is a board member) and usually order from Wes at Classicheartbeat.com (he's local to me) but I have purchased parts from all of the above and LMC in the past as well.