The Crane coil is not limited to 6,500 RPM. It's a very good piece of kit. So is the MSD Blaster 2. Nothing wrong with the stock coil 280 z/zx coil either. 

 

 

Just wanted to check back in on this and say that the new distributor solved my previous issue. Time to iron a few other things out before I can get the car done though. Seems like I've had it in the garage more times than on the road unfortunately.