Do you have more photos/ detail of your car? Transmission, Engine, Carbs, Exhaust, ignition? One of the best mods to these is to fit Electronic ignition which there is one on ebay at the moment. The more we know of what your car runs the more this site and the people who use it can help.
http://cgi.ebay.com.au/Datsun-Nissan-240Z-260Z-280ZX-Electronic-Distributor-/140414051459?cmd=ViewItem&pt=AU_Car_Parts_Accessories&hash=item20b1546483