For the most accurate parts I tend to go to Jim Carter, For the regular parts I go to Classic Parts. If I am in a pinch I go to LMC. LMC tends to be the most expensive, and there parts(other than seals and rubber) tend to be cheaper mfg items(Like the Firewall Mat).
The best shop(that I have found) for tech service and hard to find parts is Bowtie Bits in Wichita KS. They have some of the most difficult to find huck brake parts for my 3/4 and 1 ton.
I also like Tom Myers Truck Parts in Miami Ok. It is a salvage yard of Art deco's, AD's, and TF trucks. If he has to order new, he just orders it from Jim carter. His used selection is outstanding, but you will be doing the overhaul work.
American Classic Truck Parts had the best deal on the Overflow tank.
my $.02
