Brian,
Your distributor will have one of two advance limiting plates in the mech advance area- 10L / 15L, or 13L /18L. I assume you are going to use your car on the road with our lovely Kiwi paint thinner fuel and the odd club day on the circuit hopefully with some Av Gas. Unless you have been lucky and obtained a 69 351w 4v distributor you will have the 13L / 18L option. Have the electrician install this with the 13L end over the limit peg. This will give you 26 deg adv in the dizzy to add to around 10deg initial timing for a total of 36deg all in. I have a selection of Ford springs if you need them to help set the actual curve once you work out what you need to suit your engine build. Compression Ratio chosen will play a large part on what you need. I have several charts of advance curves from the GT40 era, but with the fuel quality of today these are of little use as most work on 14/16 deg initial/40 deg total.
Jac Mac
