Is your car a factory widebody??? If so, it has some rarity as a model, which you will lose by the modification you are considering.... If not, and it has been "widebodied" in the aftermarket, then cutting the targa bar will likely not make things much worse resale wise.
It does have a real detrimantal effect on stiffness to remove the rollbar and rear glass, in a car that is not very stiff to begin with. Your wide wheels and such will magnify the flexibility of this car, and it will shake, rattle and (well, it probably won't actually roll
).
My advisethen. If it a pretty nice car now, sell it and find a nice early cab if that's what you want...
