How do you tell which is the right door handle and which is the left.

Has anyone successfully replaced the threaded studs on the handles, that snap off, when the stud becomes rusty?

Look at the back of the handle to see which way the rod goes. It has to go downward. If you find you need a set, I have them and the key I think.

No sure what you mean by rod. There is a ball for a nylon fitting to attach to it. psg

Here are two pic's of the driver side door handle. Hopefully they will help.
It look like the rod is high on the round post.

my 78 has the previous version door handles. thanks. psg

"Has anyone successfully replaced the threaded studs on the handles, that snap off, when the stud becomes rusty?"

This is the Archilles' heel of the door handles and rear tail lights. On the door handle, the stud is cast with the rest of the handle and made of whatever alloy the handle is made of.

You can try and cut off the stud flush, drill and tap the hole, screw in a bolt with some thread locker and cut the head off the bolt.

or like mine
when the pass side broke i had a guy fixit

he drilled all theway throu and drilled larger holes halfway from the face
to resess the head of the new bolts

its been on for 10 years that way
not too many notice.joe

I will let you know how my fix works. I have tried to types of metal repair. The first is a material that is a malleable metal putty and has worked for one patch and now I am trying JB weld which seems stronger. I cut off the stud, drilled out a larger hole and then took a bolt and cut off the head to match the length. I wonder if brazing would work. psg

Since the handle is made of a non ferrous alloy, welding or brazing won't work. However since it's a relatively soft alloy, drilling and tapping is easy. Just clean the hole and bolt well with alcohol, benzine, acetone, or fingernail polish remover then use some form of thread locker when you screw the bolt in. Your wife's fingernail polish will work as a thread locker. Matter of fact, just use all her cosmetic products for this fix.