Lots of options. I’ve got the HEI from EBay seller TheSwapMeetParts. Other guys are running the Duraspark II setup. DUI makes a good one. I’d stay away from the A Team Amazon one because the word on the street is that the seals aren’t good enough to stop the distributor from filling with engine oil. That oil passage supplies oil to the rockers and has a fair bit of pressure.
Note: When you upgrade the distributor you will have to change the carb or modify it for a ported vacuum. The OEM carb does not supply a standard vacuum signal and is not suitable for connecting to a vacuum advance fitting on the distributor. You can just put light springs on the distributor and disconnect the vacuum advance altogether but I tend to prefer the transition from idle to acceleration with vacuum advance.