Hi Rob, i used the inner cable from an old tv lead i had laying around, ( there is more than one size, sky cable is thinner) i drilled a hole in the block where the sparkplugs should be this gives a good glueing point for the HT leads, offer up each lead & bend to shape before glueing into place.Dont paint the leads befor gluing as this will give a stronger hold.
The thing i hate about a high dizzy's is that the leads to it have a 90 Degree connection to them.
Hope this helps & you are not affended by my comment.
John
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I hope you dont think im showing off with my pic's but i to had the same problums you have but with a little out of the box thinking & help from othere's on this site a good finnish can be achived.