car stops in the wet

Hey guys, I've not been using my two much over the last few years. LARGELY because it stops when it rains.
 
id procrastinated about finding the problem cause with targa tops i avoid the rain anyway, but i finally got around to looking for it. After electrocuting myself on a wet HT lead i believe ive found the problem.
 
last time the engine got fitted i had a couple of coils sitting round and i believe that what ive ended up with is a 5mm lead with a 7mm coil.... or vice versa. when it rains the connection fills with water and shorts out.... when i grabbed hold of it, it shorted through me and the engine stopped.
 
I'm not sure if i will need a custom lead or a different coil or what (suggestions are welcome) but at least i know where to look now and hopefully if anyone else has a similar problem they find my post :-)