Yeah, 17420 won't clear headers and even some stock exhaust systems. You have to try it first and be prepared to take it back.
For your application (headers), I recommend Jegs 10081 for 186-tooth flexplate/flywheels. It's the same Nippon Denso design but can be adjusted to sit closer to the pan. It's more expensive but it works great and is super strong.
http://www.jegs.com/i/JEGS+Performan...10081/10002/-1
Another option is Jegs 10080. This one can be used with both 153 and 168 tooth flexplate/flywheels. It's a little cheaper. But doesn't sit as close to the pan because you need to use the other set of holes that pushes it out. But it is more clockable, so that makes up for it. Its not as strong, but still formidable.
http://www.jegs.com/i/JEGS+Performan...10080/10002/-1
Be prepared to switch the solenoid wire ring terminal to a spade terminal with either of those starters.