Several years ago I made the mistake of replacing the back light (rear window) in my 66 Coronet. Si,ilar to the OP's saga the original glass was concave and followed the body lines. The new glas was convex and gave the rear winow a bubble top kind of look which made the car look goofy to me. I sold it and found a 4 speed car to build. I'd rather have an original OE beater than an aftermarket laden show poodle for this reason. The cars built off of the reproduxtion parts is a representation of the original. If used as intended most of that stuff will fail.

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