Kingpins. Where to source them??

[lexadmn]

1976 C60 with F050 front axle.

I am not able to find kingpins for this truck.
I have been looking for several months with no luck.
I can however, find these parts for the 7000 # (F070) axle, but I do see in my manual - these are different all together.

I have visited all of out local auto-parts stores. Too old. Computer doesn't go back that far.
I have done Internet searches until I am tired of the Internet. Nothing.
We do not have a local NAPA, but they do not show these parts on the Internet either.
I have stopped in the local heavy duty truck shop and they tell me - too old, we don't go back that far.
I tried the Chevy dealer and they tell me - "if it is older than 2000, we cannot look it up".

Does anyone have a source to the 5000 # (F050) kingpins?

At times, I find I am older than I feel. I don't feel a 1976 truck is old, but the kids at the parts store remind me I am as is the truck since the computers will not search that far back.