Only way to find out what its angles are(with any kind of accuracy) is to put it on a digital cad machine. There is another tool that reads angles but I cant remember what the name of it is off my head. My machine shop here does helix checks for me and gives you a 3 dimensional cad drawing and your exact angles for $25 each. I get them done all the time. Its not cheap, but neither is buying more helix's and the wrong ones at a $100 each. At least this way, you know what you have and can make a educated decision on what way you need to go, before spending another wasted $100.
Really helps out on the aftermarket ones from like Bender, hauck,Maxx, where even after you buy it, they wont divulge the angles to you, I know what they are exactly this way.