The 165/80x15 tyres fit the 5" rim which is standard. I have just bought new wires for my 4/4 and bought the 5x15 stainless from MWS. In fact I also opted for new tyres, as I had a buyer for my chrome wires and it suited us both to leave the tyres on.
You can, I am told, fit those tyres to 5.5" rims, for example minilite alloys.
I would ask two questions:
1. Why buy wider wheels anyway? The 5x15 wires are considerably less expensive than the 6" ones, and I can't see any advantage if you intend to reuse your tyres. 5" wheels and suitable tyres are lighter tahn 6", and the car really doesn't need wider rubber for traction as it is only 800kg.
2. How old are your existing tyres? Even if only part worn, if they are over 5 years old you should probably replace them as they harden and can fail. New Firestone F560s only cost me £50 each fitted.
Finally, the MWS wheels are great quality and are now tubeless (if you didn't know that already). If you ask Charles Americanos (at MWS) nicely and mention the MSCC you should get a discount on a set of 5 - I got 10%.
Have fun
Nigel
