When I had a 440 6bbl cast iron dual point distributor (with the Mopar Perf height adapter) in my '67 Newport 383, it ran generally good, but I never could get the points adjusted to get the extended dwell the dual points should have. One night, I pulled it out and set it up in a vice and measured the point gap with a dial indicator. THAT's when I discovered that the lobes on the distributor cam were worn enough that if I set the gap at spec, the dwell would be off, and vice versa. THAT's also when I bought a Mopar Perf conversion kit to replace it (back when their kits were better than they now are). End of story.
Bad thing was that few of the lobes' peaks allowed for a "good" point gap to specs, which I'd never considered to be an issue. Back then, we just put new points in, lubed the lobes with the cam grease that came with then (in a small plastic vial), set the gap (on whichever was the closest lobe peak), and all was well. Sometime in the 1980s, that little vial of lube was not with the point sets I could find locally, which also tended to coincide of others with points not getting 10K miles out of a set, by observation.
The OTHER issue with points is that they exert a spring pressure on the upper dist shaft bushing, unlike the factory OEM electronic distributors where the shaft just spins. That wear might cause an issue if the bushing is not renewed.
There can be a bit of additional wiring that will need to be run, plus one of @FURYGTs electronic voltage regulators is needed too.
Are the spark plugs and plug wires recent, too?
When it's all done, it should be great to drive that 300L again, I suspect.
Just some thoughts,
CBODY67
