Need help. 300ex no spark

Sorry for this thread again i know its been up here alot .. So I'm workin on a 300ex rn , when I bought it the guy had replaced everything eletrical but the solenoid. I went ahead and replace it ran some more test I'm getting 12v everywhere. To the cdi, reverse unit, switch . Everything seems to make good power but still no spark to the plug . The only few things that's not hooked up is the saftey switch , reverse switch, and the indicator bulbs for them .. I seen how to bypass the reverse inhibitor but my reverse wire (GRAY ) has 12v running thru it , so how am i suppose to safely ground it the frame without burning anything up..