9J Porsche Alloys on Type 2 Camper?

[73 Westy]

I need help/advice in trying to fit a set of 17" cup 3 alloys on my lowered 1973 bay window camper.

Rears are ET47 9J/17/h2
Front ET52 7.5J/17/h2

I have got 20mm adaptor for the front which I hope will be ok, but it is the rears will be the biggest problem so any ideas would be welcome.

I thought that getting the hubs machined to 130 pcd and fitting a 225/45 tyres would save some width! She is lowered by 1 spline, so

1 What size of spacer will I need to clear the spring plate
2 how do you flare the rear arches if necessary?
3 What length of studs will I need.

Any advice or links would be very welcome.

Thanks

David