Thank you, this got me excited. However when I called Parts Geek to verify that the bleeder comes with the Raybestos wheel cylinder they said it does not. 

Thanks, I'll check that out. I assumed the entire series of these trucks were metric

I noticed Beck Arnley made a wheel cylinder for the 1976 models that includes the bleeder. The wheel cylinder has a different part number but the parts catalog indicates the bleeder is the same as a 78 so I ordered them. I'm not counting on this to work out but that's the chance I'm taking

Thank you, good to know

On ebay I'm only finding the bleeder screw. Can you provide a link? Many thanks for the reply.

I did see this one for 79 dollars:

Thanks!

I bought one of them.

Yesterday I bought 2 wheel cylinders from somewhere else that appeared to contain the bleeder. If I knew about your discovery I would have bought both from ebay. All of these are for the earlier 620 so I'm hoping I can detach the parts that I need and they will fit the proper wheel cylinders that are already on the vehicle.