You're saying the engine spins over just fine but doesn't fire?
If so, you need to go through every component in the ignition system and replace or repair it.
When did the hard starting begin? Did it start easily in the summer and then stop starting in the winter? Did it get harder to start gradually over time?
First thing is check points gap and/or replace the points. Gap plugs, check plug wires, cap, and rotor. How old are all those components?
Have you tested to see if you're getting spark at the top of the coil? What about individual plugs?
What about your condenser? Those are notoriously bad even when brand new. Go to the electrical section of this forum and read the articles pinned at the top of the forum on the new condensers posted by Jon G. He makes 200,000 hour condensers that actually work.
Make sure your timing is set properly.
How long does it typically take to start? When it finally starts, does it run properly?
When you hand cranked it, did it start and run?
