I recently bought an Accel Super Stock performance coil and it has given me a fairly reasonable performance increase, maybe only 4 or 5 ponies but it really helped to smooth out the acceleration and idle of my engine. I'm sure there are better of higher voltage coils out there but for $30.00 at Advanced Auto It was well worth it.
Pertronix has FlameThrower coil. Its a 40,000 volt coil. Runs around $29-33 depending on if you want it black or chrome with shipping included. Here's a site that sells them http://www.vintageperformance.com/retrorockets/coil.htm I'm running that along w/ the Pertronix Ignitor, eliminates the points on dizzy, and its been hassle free.
I just replaced my coil with an MSD Blaster 2. I paid $40 for it and the owner of the speed shop suggested it above the more expensive coils sitting there along side of it. Anytime someone does that I figure they are giving me good fair advice. Good luck. John