I have had the Crane XR700 ignition installed on my (B20) 122S for the last 7 years without a single problem. It cost $A250 here but is no doubt cheaper in the US. It sure is worth the money as there's no more points maintenance or dwell variation from your worn distributor shaft. You will find that your engine is much smoother. The kits are generic and the parts fit my Bosch distributor fine. I used the OEM coil so no other parts were required. I run a modern tach which has no problem with the ignition signal but I used the XR700 in a 1800E some years ago and the Smiths tach didn't like it at all.
Installation was pretty straightforward for someone like me with average skills and I found the instructions very easy to follow. You will need to remove & replace the distributor so, if you can do that, you can probably do the rest. I asked an auto electrician to quote on the job and they said $80. I don't know about the other systems mentioned here but my experience withe the Crane XR700 is 10 out of 10.