I've had the Taiwan chromed steel pent roofs on my Cobra for 12 years and no rust...of course I do polish them a few times a year. If yours leak
oil, you're tightening them down too tight, warping the steel. I do use gizmos that spread the bolt force over a larger area, long ones on the top & bottom and triangle-shaped on the corners. I will agree that aluminum covers cause fewer problems for most people. Chrome steel covers will get minor scratches...not necessarily through the chrome, but the plug wire separators (plastic!) will mar the chrome if you're not really careful when you remove the dist. cap or whatever, and you can't polish them out. I haven't had any problems with the chrome other than what I mentioned, and I might add that the cost of having anything chromed is the polish work involved; any imperfections have to be polished smooth before it can be plated. The actual plating itself isn't expensive.
I remember seeing pictures of the 427 with pentroofs in mags when I was in my teens and thought it was a beautiful motor; that's why I've got them, I like the look, "warts and all".
My 2 cents,
Dan