About...oh...13 years ago, Dean Marcum of the BGNRA had a lot of discussions with NHRA Div 7 about bolt-in rollbars. We were dealing with the fact that most of the NHRA Techs at the time had no idea that ANY street car could run 11's. Anyways, because the G-body is actually a semi-full frame car, they said go ahead and do a genuine bolt-in like every other sanctioning body (SCCA, the eruos, etc.) accepted and often mandated. So AutoPower of San Diego did one for me (used my car to design a bar for g-bodies.) It's the real deal with removable side bars, etc., plates above and below the floors. Not the kind of thing you put in and take out for a weekend of racing. It's in there, but can be removed for upholstery work, etc.
Think about it: if a body-frame separation is the concern, wouldn't you rather have the roll-bar stay in the body with the driver?
Mac
In theory, that sounds good but do you think the body would come off around a frame welded rollcage. I think the body/rollbar/frame would be safer.
Just my opinion.