63 BUICK Skylark stud pattern / wheels?

So my old man has a 63 Buick Skylark here in Australia, as there are not many about i was hoping that i could find some answers here.
It is a 4 stud car and has 15in wheels that are to big as they catch the fender lips. We would like to go down a size so.....

What size did they come with from the factory?
Other models or makes that shared the same stud pattern?
Any stud pattern adaptions done in the past?

Any sugestions would be great
Kyle

 

They came with 13" from the factory. I think they are 4 on a 4" bolt circle, but measure it to check me. That is not that uncommon a bolt pattern , but only shared with Olds F-85 and Corvair in GM. Look at old British cars, Ford Falcon and small Mustangs, etc.....

 

4 on 4&1/2 I do believe. Also early Chevy II used them.

 

I suspected the corvair, but they are just not around here, perhaps we need to look at some japanese makes.
They are very similar size pattern to ford falcon but the studs are smaller diameter.