I had a similar problem a few years back on a VL commodore. It would start out slowly by the tacho bouncing a bit irratically then the car would start to stutter and jerk, mildly at first then worse. Everytime i changed something it fixed it but only for a few weeks, i changed, leads, sparkplugs optical pickup in the dizzy, fuel filter etc. It went on for months, i was fukn ropable. I never took it to a mechanic but a mate that is one had a look and was just as baffeled as me...i wouldnt call him a gurp mechanic though.

Anyhow i found the problem, a loose terminal on the coil, everytime i replaced anything i checked all the conections were on tight incase i had knocked them off installing anything and i would push the conector on which would give me another 2 weeks of hassel free driving. I put a new female spade connector on and the problem went away. I was stoked but fukn pissed i didnt think to look at it sooner and before i spent a couple of hundred bucks on parts.

So maybe your problem is an earthing/wiring issue?