340 Not firing on all cylinders

It did run before, (only on 6 cylinders) didn't it? Wiring looks like a challenge, but I would start to inspect the area where you've moved stuff around (distributor) check for loose hanging wires or broken connections. Are you sure you put the ballast resistor wire (the iffy white one on the picture) back on the coil plus side?

First I would bypass the ballast resistor like 67Dart273 suggested, just alligator clip a wire connecting the two terminals together, only do this for a short test, don't leave it on there for 5 minutes LOL, If it starts, you'll know there is a ballast resistor issue.

the brown wire that's coming from the ballast resistor, is that other end not connected to anything? (see picture)