When I put the rollcage in mine, I bolted and welded it. You should take the entire interior out unless you want sparks burning it. The two points that came to the front on mine, I just cut a bit of the carpeting away and it looks fine. Same for the points that go straight down. For the points that go back, the rear seats were affected minorly but it still looks good. It all depends on how much time you want to put into it. I've seen pics of a mustang SN-95 that had put the bars through his dashboard but it looked really tight.
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Blueneonman - '95 5.0L Mustang GT Convertible | K&N Drop-in | FMS 9mm Wires | Hollow Cats | Flowmaster 2 Chambers | Subframes | 6-pt Rollcage | 14deg Timing | King Cobra Clutch | FMS Adjustable Clutch Cable | Coolest Neon Lighting on a Mustang EVER!
Homepage:
http://www16.brinkster.com/blueneonman/
Best time: 14.719 @94.87mph