Did you get this sorted? I have a 17" snowflake sitting in my bedroom and also several photos of the inside of the rims when new, don't look much different to stock 15". Just measured....the centre of the hub hole inside the centre cab has a 45-degree 1/4" chamfer.
And no, they take the stock snowflake lugnuts not tapered acorn style, not suitable for alloy rims without the hardened inserts. Is the problem basically that the replacement rear disc 'hub' is thicker than that of the original brake drum so not enough to hang the rim on to centre? Any questions, photos or measurements, let me know...rim is right here ------->