I don't believe any dealer wants to see your truck in service. Understand also that you essentially have a non us spec 40 year old truck and parts are long since discontinued. Toyota service departments are there to make money not have a truck you can't use off the shelf parts on. None of the mechanics will understand the engine and the parts guy will laugh when you want to order a sun visor. You should visit the 40 series section for parts questions and find a local mechanic first. The diesel folks here might help with engine diagnosis but transmission - axle -etc is best served in 40 section.
They dont sell diesel powered vehicles, so they wont know where to start. They are so simple to service, you are throwing money away letting someone else do it. They can go for decades with just oil and filter changes.
I agree with Rick, the 40 series folks will know more about parts acquisition than anyone else.