I no long am so sure what to recommend for conversion. Parts store quality is changing for the worse. I still really lean towards a Mopar breakerless distributor triggering a GM HEI module. Whether you upgrade the coil or not, you can eliminate the ballast resistor and this will give you a hotter spark.
Many guys have good luck with Pertronix. I say if you go Pertronix, buy two, so you have enough spare stuff to fix it on the road. That's because you can't buy spares everywhere.
If you can find a couple of clean junkyard Mopar ECU's cheap they work fine. Not sure I'd buy new parts store ones.