I'd expect the angle to be pretty standardized on Cobras with LeMans hardtops, for the roadsters, pretty much whatever you can get....
This is not an original Cobra either (it's my ERA 289 FIA). The holes in the base of the windshield frame were fairly large, allowing quite a bit of adjustment (I may have hogged them out a bit more...can't recall, it's been nearly twenty years). Adding this much rake to the windshield will affect the shape of side curtains and soft top, if you have one. I had to modify my top bows and tonneau cover to work with my windshield angle.
Jeff