Minimum Center Bore size of 14 Bolt FF rear axle

[Getter-Done]

I am looking to have a spare stock set of Tires and Rims for my 84 C-20.

Currently it has 36 x 10.50 x 16.0 Super Swampers on it.
The center bore is 5 1/8" Diameter on these 10" rims.

I want to get a set of rims 6.5 x 16.0 rims.

I know some of the van and 2wd rims will not fit this axle.

What is the (Factory) center bore Diameter,
I need for a 14-bolt full floating rear axle?

I have a Corporate 10 bolt in the front.