Just to update this thread, I had the 90 at the local garage for a few days so they could run diagnostics on it.
The finally traced it back to a bad coil. Weird as I've heard that coils don't usually give up ghost so quickly (I had installed that Mallory coil with the Mallory dizzy last April). I don't know if the coil had something to do with the cracked in half ballast resistor or vice-versa. They said the coil was leaking into the wire and when I shake it there feels like fluid moving around.
Seems like when the engine bay got hot the coil would act funny and give up. And only hot enough when the hood/bonnet was down.
So there is a Lucas coil in there now as that is what the shop had. Seems to be running better (and I don't want to jinx it
) but I noticed in first gear and in reverse I can let the clutch out now, at idle and brake lightly and it runs more smoothly than before.