Sizing up some Rear Wheel Spacers!

[Ditchdigger]

Lookin at getting Rear Wheel Spacers for my 84Blazer.
What is our Hub diameter size, (The hub inside Bolt pattern)?
Ours is larger than newer Chevys correct? starting in like 88 or 89.
Would it be 77.8 MM Hub Size?

 

[Ditchdigger]

Anyone?