Sort of made up my mind now. If there are no objections I'll go for the MP 4529795 Ballast Resistor:
http://www.summitracing.com/parts/dcc-4529795/overview/

Strictly speaking a four prong isn't needed and certainly not used by the ECU but it'll snap right in and look correct. Matter of fact I still have a spare Standard Motor Products RU12 lying around but no idea what resistance that has. I *think* it's 1.5 ohm, which would be close to the MP one.

For a coil the Pertronix FlameThrower sounds right, I'll keep the Blaster 2 as spare though.

Maybe I'll change everything for a computer controlled ignition in the future. No doubt light years ahead of the Mopar stuff but for the time being I'll just tweak the existing setup.

Thanks everyone!
Tim