Lots of options. What are your goals?
Adding more initial advance (from 2* to 10*) and limiting total advance to 30-32* (initial + mechanical) noticeably helps the low end power. Add lighter advance springs to get the advance in sooner helps too.... up to a point. Too much advance too soon and the engine will ping.
An adjustable vacuum advance from Crane can fine-tune your part-throttle advance to improve economy.
Easy way to get the 10* to 32* mech advance is to find a distributor from a 425 dual quad engine or an earlier Dynaflow-equipped 401. Without that special breaker-point plate, you'll have to either weld up the advance slot or put an offset bushing in it. Tom probably knows more methods.
A nice one-wire breaker-point replacement is avail from Lectric Limited. I haven't used it, but many recommend it.
http://www.lectriclimited.com/breakerless_se.htmCrane has a version as well, the XR-i. Features a rpm limiter.
Petronix has had several versions, I'm not up to date on their offerings.
I'm still running a Mallory Unilite in my blue '66.....over 30 years now!
Someone was offering a HEI converted distributor for Nailheads some years ago, unsure if he's still offering them....
If you want more features like a timing retard, rpm-activated switches for shift lights, nitrous, etc, or even a fully programmable timing curve, check out the offerings from MSD, Crane, or Mallory.
You can even mix components.... use a GM Hei magnetic trigger to fire one of the above mentioned boxes. You can fire thos boxes with points too.
What ever you end up using, it's always a good idea to have a good ole points setup in the trunk just in case your electronic setup gets fried!
