Hot Rods Spindle diameter??

So…went to mock up my brakes tonight and come to find out the round back I’m using has a 1.3” diameter on the inner bearing surface compared to the stock 1.17 or so. Anyone ever seen round backs with a larger shaft? I guess I’m in the market for a single round back driver side…this is a first for me. More curious I’ve messed with a lot of spindles and maybe lucky or just didn’t know they made different sizes?

 

The one with the large inner bearing ID is probably from an '37-'41 F3 and larger truck.