Bizarrely I have been struggling with the same confusion with my v8 conversion. Ticked over fine but miss fired badly when taking its first trip to the MOT.
The car is running the Range Rover electronic ignition with 12v coil but with the original Magnum loom. It seemed to run better on full choke but was miles too rich. This lead me down the path of carburettor strip downs, fuel pump testing etc...
After no fault was found I moved on to the spark and found it was irregular. weak and yellowish.
I trawled a few forums for 'Weak spark' and it dawned on me the original loom had a ballast resistance wire which was incompatible with the 12V Coil and Ignition Amplifier.
It was getting late on Sunday night so I jumped a 12V supply to the Coil from the back of the Alternator and immediately got a big fat blue spark and a revving engine without a misfire.
This weekend I will wire it up properly and see how it runs
The next day I logged on to this forum and read this thread.
Paul and I seem to be living in a parallel universe
This is what forums are for.