Have you done compression test?

If you disconnect coil and crank it does it sound even on the starter?

If it turns over irregular on the starter it points to lack of compression on a cylinder, hard to explain...

Have you checked if it's advancing timing (vac advance if fitted).

When you say you've checked timing, do you mean cam-crank as well as ignition timing?

Are you getting and keeping battery voltage at coil under load?

What makes you suspect alternator, is it charging OK?