this should be worth very sensilbe money.
Whatever happens, it'll be the right thing. you know the gt3 will sell inside about 30 seconds. I've no idea if the vauxhall Chevette is popular?
You can now get new ones for less
https://www.torqen.uk/nissan/240z-260z-280z/engine/ignition/246366-electronic-distributer-new-complete-l6-240z-260z-280z-280zx.html
theres a P1 here, its a couple of quid though.
https://www.tomhartley.com/used-car-details/used-mclaren-p1-v8-coupe-mso-graphite-grey-automatic-petrol/id-4230/
its got to be worth a solid £25k. given what you'd spend to make it 'perfect'.
at that money it'll make a nice rolling resto. 50 year old dampers/brakes would be the first thing i'd throw fairy dust at.