not louvers , and not meaning to hijack , but I just saw a car on the road I had forgotten about, haven't seen it in 10-12 years - it is a 1970 Cuda convertible, 340 - 4spd , F8 (I think), white hockey stick stripe, with 71 Cuda gills in the front fenders. I remember speaking to the owner when I first saw the car - he told me he loved the 71 fenders and had a body shop do the cut outs and installed NOS fender gills - this is now probably 20-25 years ago or more - he might be the original or second owner - I forget - this was before anyone was stamping, cutting or anything . The worst part is that the body shop did the cut outs in the wrong spot - they start over the wheel wells - too far forward - it is what it is - he did it when the prices on these cars were next to nothing - and it's his car - I'd say do what makes you happy - I happen to love the look of the rear window louvers !