The shocks will be just as bad with a fiberglass lid as the torsion bars would. In fact, when GM did the fiberglass hoods on some of the 3rd gen Camaros, they spec'd a lower pressure shock just for that purpose. I would think about trying to retrofit the torsion bars to the Regal instead of keeping the shocks. In fact, it was one of the things I had checked on my Cutlass when I got it to be sure it did not have them. The torsion bars can be de-tensioned by moving their mounting position down a notch or two. There are 3 or 4 positions from the factory to allow for this.
Also, anyone who wants the aluminum G body hoods should be aware that the hood springs are lower tension on these too, and remember to take them when you get the hood. Failure to do so will result in bending the hood in half!