If you say the engine doesn't "crank," that suggests that the starter is not rotating the engine when you try to start, which, by the rest of your post, doesn't sound like your issue. Assuming the engine "cranks," but doesn't "fire," I would go back to your "weak spark" issue. Did you check your spark with a spark tester which allows you to check the spark voltage? Make sure your spark plugs are not gas fouled. Make sure you have clean and tight grounds for the EGI harness at the intake plenum. Install a noid light to make sure the injectors are firing. Check your compression. Verify proper fuel pressure. This all assuming you timed the distributor properly.