Is the 6500 left (front der.) shifter pretty much the same as 6600? The shifters are both doubles, but I don't think it would matter if they were tripples. My mind tells me yes, but wanted to double check.
Outside of the shape, is it safe to assume the functionality to be the same? I don't think the double/triple matters. I've used triple shifters on doubles without a problem. This will be used in a double application.