Setting ignition timing before first start – advice please

I’m soon going to start my Mustang engine for the first time after a re-build – I have fitted electronic ignition (Crane XR-i) and I need to know that the distributor is in the right place (good enough to start) so I can then adjust with a timing light once running. If I had points, I could use a 12V lamp to get the initial timing set, but with electronic ignition how would I do it?
 
After setting as Limey recommended, leave the distributor clamp snug enough that the distributor won't rotate on its own, but loose enough that you can adjust it by hand. Have a helper turn the ignition while you make modest adjustments to the distibutor position. Play it by ear for the first position, get it running, then put a timing light on it... :D