If it's of any use as a clue...

When you try and drive it as is, at really light loads it'll miss badly, but enough that you can get it to 30-40kph. Try and give it any more and it will backfire, loose all power. Within about a minute of driving it'll degenerate to the point you can barely make it do more than 10kmh without it missing really badly....sounds like ~50% of sparks are being missed.

You haven't developed some sort of vacuum leak or something of the like have you? Something that is messing up the mixture enough to ruin your plugs fast? Check the vacuum hose and the fume one that goes from the block very closely. Something llike that can come on suddenly.

Nah, they're all fine. It's over at my mechanics now.

He's pretty busy so might be a while till he gets to it.

Hopefully he can figure it out.

Justin, I feel for you! I had a similar problem when I was going through my 240. Now I'm not suggesting this is your problem, but my problem turned out to be a worn out centrifical advance mechanism in the distributor. It would run like crap and hardly idle. Once above 3000 rpm it ran perfectly. The strange thing about the whole deal was that I went through three distributors and all three exhibited the same problem. Finally purchased a Mallory Unilite distributor and all has been well since installing it. Hope your problem gets resolved soon....good luck buddy!

Interesting. I've heard of a few similar things now that have had a really wierd fix.

Still at the mechanics. He's pretty busy so hasn't had time to get to it. Can't wait for it to be up and running again. I'm having withdrawal symptoms.