Buddy heard chattering from his gearbox, we dropped the oil pan and found gear teeth laying in it. We split the case and took the gears out and found this:

Gear from the main shaft

Gear from the counter shaft

Ordered what was needed.

But now an old timer at work says "it's not worth it since the trans blew and it being a shared oil system." Which makes sense, but if everything is inspected and looks good, I don't see any harm in it. Thoughts?

 

The old timer is correct I suppose. The broken teeth that you found in the oil were they intact or mashed up? can you account for all missing metal work. If the case is already split you could try blowing out all the oil channels and see if you discover more bits, would be a shame to condemn the complete engine and the cost associated with that.