No spark? Being on this thread, I presume you have gone to HEI. I had an HEI burn through the rotor by not hooking up the second coil ground in the cap. It would spin, no spark. It ran one day, nothing the next. Look for carbon trails on the rotor and a burn hole where the carbon goes to the rotor contact.
Second, I had an HEI that had a cracked wire to the module. When it was wet, or very humid, the wire would not carry current. I found it by pulling the wires and it would run. These wires go from the harness to the distributor. I later changed the module and found the crack in the insulator.
On my old dual point distributor, I had glazing over the points. I filed the points and she went off. I later fixed the glazing issue, a rebuild, and changed to HEI.
Good luck, I know how frustrating it can be.