Factory Wheel Center Bore

I'm going to be ordering my Cragar/Rock Crawler/US Wheel "Soft 8" style wheels pretty soon. I listed all three brands because they're offered in different backspacings (3.75" or 4.00"), etc. I'm not sure what one I'm going to go with yet.

I done a search, and I couldn't find what the measurement is on our factory center bore. I don't want to get one too big because I don't want the weight to be resting on the studs. Anyone have any idea? Most of the aftermarket wheels I've been looking hat have been geared toward Jeeps (the 4.00" BS). IIRC, they had a 30mm center bore. I read somewhere that a Jeep's center bore was too small for our Xs...




EDIT:

I came across these wheels the other day... they might be an alternative to the Soft 8's.]

http://cgi.ebay.com/ebaymotors/EAGL...0QQihZ018QQcategoryZ43955QQrdZ1QQcmdZViewItem

 

[CDW6212R]

I don't remember what it is, but I've found it twice on the internet. Google for "center bore" and "Ford", good luck.

 

[X6StringerX]

I've Googled similar arrangements of those key words and all I get is information on the engine bores.