I'm hoping to do a write up soon in what should be the "ultimate" ignition on a sane budget ~£50 if you already have an SD1 type distributor.
Can't claim it's my original work but it beats all commercial systems by using an 0.3ohm E-core coil without a ballast. Most of it is stolen from what the US old car scene does. That is regardless of whether it's a Ford, Chrysler or GM car, they all switch to the GM HEI module - because it is bulletproof and just better. But if you read up about it it's been done to everything from a Rolls Royce to a FIAT X1/9. Even a Yugo. It's so cheap and so flexible in application. Which is great as it is £20 and can easily be triggered from the SD1 dizzy. It's actually what Lucas stole and wrapped in an expensive aluminium case for the Jaguar V12 system and asked £400 for it... This type of system was common until the early 2010s when coil packs took over pretty much everywhere. Remember ignition systems HAD to get better in the catalyst era because misfiring or part burned fuel would contaminate it.
What makes it good is two things. The module isn't just a transistor switch as most modules you'll retrofit are, it has an active current control which eliminates the need for that fixed resistance to avoid cooking the coil - higher end systems will do this but cost £100s. Due to the characteristics of an inductive circuit, they initially present a high impedance when switched, the last thing you want a any more resistance, this costs at higher engine speeds as the coil simply can't charge fast enough between sparks. The second part is simply enabling the use of an E-core coil means ~1.5-2 times the energy transfer as the design is more efficient than a canister coil. And it is spark energy that is important. These sports coils which boost the voltage are only good to a certain point. As a bonus you also can't cook the coil by leaving the ignition on and the thing runs cooler because it is more efficient.
Here's one write up of another car but the principle is the same:
HEI Ignition Upgrade
My system is part installed as I haven't yet fitted the e-core coil as it uses different ignition lead terminations.
BTW I generally recommend US made coils. These typically run V8s for decades. I have currently one from Taylor Cable.