Where to buy big truck parts

[Lynn]

Putting 350 engine and 5 speed trans from a 1972 C50 into my 49 Studebaker farm truck.
Not exactly and LS conversion, but still an upgrade from the flathead six and crash box.

Motor mounts, clutch parts etc. are all different than a pickup truck.

Specifically, I need the clutch pivot ball that screws into the bell housing. Looks like the one for cars and pickups but is bigger.

Standard one for cars is 1/2 x 13 thread. This one is 9/16 x 11 thread.

I know some of you have some big truck experience. Any good source for parts?

Any help is appreciated.