This is it:
http://www.sweller.dynalias.org/images/DSCF5070sml.jpg [1]

I've had a fair few positive earth cars in the past but converting
this one maybe a bit tricky.  The clock isn't fussy about polarity (as
the parts books give the same number for both types) and the tacho
relies on a small AC generator which is isolated from the rest of the
car electrics.

The fuel pumps are the problem, they seem to be polarity dependent and
they're not cheap - are they something that could be readily converted
or is it bite the bullet and buy two negative earth ones?

Getting a positive earth radio with FM is a bit of an arse.

[1]  see that, that's a subtle bit of willy waggling.