From what I've heard from some of the SHO people here before, most insurance companies don't recognize the SHO as a performance vehicle, just a trim level and the insurance difference wasn't much of anything. Definitely need somebody to verify that, though.
I can't say for sure, but our insurance company thought my brother's 4-cylinder Sunfire was a "sports car" because it only had 2 doors... whereas, as far as I know on my SHO, I don't pay a premium because of the model.
Although the guy who gave me the loan for it said "SHO... that's fast, isn't it?" to which I simply replied "oh, yeah..."
Try going to someplace online like Progressive or GEICO, put together quotes for two Tauruses, both of the same year, but make one a regular and one a SHO, see what the results are.