Channeled 91
Manic Mechanic
This is what you should have on your tail shaft.
Note: it says the hole in the yoke is a vent. I would think if it was plugged you'd run the risk of blowing out the O-ring and starting a leak later down the road...
http://www.73-87.com/7387garage/drivetrain/yokeleak.htm
Here's where you can get it...
https://www.ebay.com/i/311278744322...MI_LemiPHM6AIVjsJkCh0q0QkOEAQYAiABEgLzT_D_BwE
thanks I just ordered part on eBay.