Distributor Shorting!

Firstly thank you to all who helped out last time. I kind of have the problem sorted except for one piece.

So initially my 110 V8 petrol 1989 was not starting. No spark nothing!! Replaced the distributor and she kicked back into life. Except now the same thing has happened again. The mechanic has told me the problem is electrical but I cannot seem to find out what is shorting the distributor?

Any suggestions?

Thanks