Steve,
Like you, I first tried a pre-cut kit and it didn't work at all. I then ordered a do-it-yourself kit with straight boots at the spark plugs. They wouldn't clear the headers. I then got a 90 degree MSD kit and it worked fine. I wasn't aware of a 115 degree boot, but that might work, you just have to clear the headers. The 90 degree boots work fine.
-Bob Woods