Mic,

Verify the correct spark plugs are installed. A lower heat range will affect starting, also, make sure the distributor is correct. If you installed an assembly, maybe a crack in the cap. Do you have what looks like a capacitor mounted around the distributor? Should this fail you will have no spark. Before you drive yourself crazy, start back at the basic. Have you changed the fuel tank, air cleaner condition. I have seen an LP tank seem full, crank the bleed screw and nothing but water comes out. Good luck.