Rear wide body on 180sx

[thetopcow]

Hey Everyone, this is my first post on Zilvia and I have a question my brother and I have stumbled on for a while. Mostly because neither of us are body guys, though i am goin to school for it.
Ok, so i am looking at getting a wide body kit for my 180sx(you know like the GTP one or B-Magjc,either way it doesnt matter).

So when you are mounting these what is the best way?(rivets and then fiberglass filler to mold it in,etc)

Also the biggest "?" of all, do you cut the stock outer portion of the wheel well off(aka the lip) and then weld in some new metal(you know so that the new wider tires dont rub when the car is lowered)? cuz i want the rims to come right out to the new wider fender wells.

thanks for any input you have it is much appreciated. the other great thing is, if this is what i should do, it will get rid of some good old Nebraskan highway salt rust.