help me calculate fenderwith

[tom'72]

here's the deal, I'm running stock type 1 discs up front , porsche carrera discs in the rear on a standard automatic chassis.

wheel dimensions: front=18x35x8,5 ET56
rear= 18x35x 10 ET50 (come from a Porsche GT3)

I'm putting together a chassis with all of this, up front I estimate I need 30mm spacers on each wheel to clear the suspension and that would mean front fenders that are about 6 cm (+/-2.3") wider fenders.

In the rear I need 2cm (+/- 3/4") spacer on each wheel to clear the torsion plate.
I'm not sure but I think this way the rear wheels would need only very little wider then stock so my only option would be to get the front beam shortened.

Am I thinking in the right direction here or completely off?
What are your thoughts?

[speedy]

up front i have 2" shortened beam lower spindles 20mm spacers 17x7 et 50 wheels and 30mm wider fenders and they fit , the spindles add about 10mm ,2"oversize fenders should be ideal for your application , ibelieve sandeep has the same offset wheels on the front of his beetle with a narrowed beam and 2" fenders , on the back i have irs porsche steel arms ,17x8.5 et 56 wheels with 255 tires 25mm spacers and 60mm over rear wings and they fit ok , i would be suprised if you could get those wheels under standard wings at the back ,i would just get 2" overs and spacer up to them
cheers jon