help 1964 Slant 6 tune ups specs

I have been thinking more about doing this HEI conversion, and I do realize that I need a newer electronic distributor. I looked up a 1979 Dodge Aspen on Napa and Rockauto, of course, with a slant 6. These are re-manufactured with several different part numbers to choose from. These are in the 50-65 dollar range. Are these an ok choice, and what is the difference among the different part numbers, the only thing I can see is some come with a vac advance and some do not? And, some come with electronic chip and others do not?