...Right then,it would be a relatively simple job,to rig a start/run set-up. I take it you will have a run "switch",and the push button is to enable the starter?
This push button,would be wired through a simple interlock,consisting of a relay,whose coil is activated by a "running signal",usually the charge light,or similar. That is to say,when the engine is running at a speed high enough to extinguish the alternator warning light,the relay switches,and prevents the starter feed from energising the starter motor solenoid.
What V-8 are you using? I had dozens of these,in the happy days of banger racing SDI Rovers,i also put a P6 3500s V8 in my own series IIa ex-army wireless landrover.
It was the 10.5:1 cr engine,which was specced to use 5 star fuel...anyone remember that?
They were a copy based on the Buick engine,and were fantastic. Stretching oil relief springs,to raise oil pressure,and dressing rope oil seals on the rear-mains,was bread and butter stuff...