Do you need to tub the firewall to fit 18's??????

I've got a 91 extra cab I'm preparing to bag and I'm getting ready to buy wheels and I'm wanting to fit 18's.
Will I need to tub the firewall for these to fit when its layed out?
Also will I need to modify the brake booster?

Thanks
FLT04

If you don't Z the frame, you won't have to tub the firewall. If you make your truck actually lay flat, then yes you will.

Thanks man
Its hard enough here in Australia to bag a vechile yet alone start cutting into the firewall.
Thanks again.

ya you'll just need to bang some spots back with a hammer.