Very interesting. It is common to call them 'Mags' even when they are made of other materials. Of course there is a slight chance they are magnesium. I think you will be able to find out.
I found an ad through google that says the bolt pattern is 5 on 4.25". If so, that's inbetween the diameters used on North American Chryslers. Ours are 5 on 4" with 7/16" diameter studs, or 5 on 4.5". People abreviate SBP (small bolt pattern) or LBP (large bolt pattern).
That's good. You can do some measuring on your car with the rims before buying the tires. Put a jackstand under the front and measure hom much distance clearance it will have to the closest points of concern.
You're welcome and thanks for sharing. The front looks more like a Charger or Austrialian Valiant. Neat.