Correct ballast resistor

Are you still running a 5-pin control unit?

Many replacements are 4 pin, which don’t need the dual ballast resistor.

Time for another anecdotal story……
Before I installed and MSD ignition in my car I was running some factory 5 pin ecu and wiring I had removed from a car at the bone yard.
I had been using it for years, never an issue.

I had installed a high revving 340 in the car which had an intermittent ignition miss at high rpm.
This was over 6700, which was higher than any other engine I’d had in the car.
When the 340 went in, I also used an MSD Blaster coil, which I had mounted on the intake manifold.
Previously I had always used the big yellow Accel super coil.
Swapping back to the super coil showed improvement, but did not eliminate the miss.

I checked the voltage at the coil with the engine running…….about 3 volts.
“Ah hah”
So I started probing the wires……..the closer I got to the firewall connector the higher the voltage, but even right at the connector, the wire feeding the ignition was only like 11 volts.

I peeled some insulation back, and the copper strands were all green.

I already had an MSD 6 on hand, and since the main power feeds for that bypass all the factory wiring, I installed it.
Problems gone.
7500 miss-free rpm.

That’s the long way to say, I’d suggest checking the voltage at the coil with the vehicle running.
If it has the correct style coil, and the voltage is between 6-9 volts, I think you’re fine.