Help needed: what it takes to fit 18x9.5 et34 on E36?

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I'm looking to purchase a set of wheels that come in 18x8.5 et30 for the front and 18x9.5 et34 for the rear. Now, I'm pretty sure the fronts are okay as is, maybe a little rolling would help, but what about the rears? I know they won't fit as is, that I'll need to mod the rear, but to what extent? Do I need to just roll my fenders? Do I need to cut the lip? Do I need to add metal and flare the fender more?

What size tires should I be running?

Thanks in advance.