I’d be using old spare wires rather than having a complete loom flopping about, and giving you headaches if gremlins appear. Furthermore, you’re less likely to damage your loom through shorts etc with open connectors touching the frame.. whatever.
Battery negative to the engine block, using a heavy earthing wire…. eg the OEM one.
Battery positive to the 2 black coils wires. (can be typical loom size wire). Don’t need a switch, eg twisting wires together will do. IMPORTANT….. if not using a switch here DO NOT leave the coils perm connected for any significant time as a coil might burn out.
Coils wires Yell / Blue (as normal) to their respective points plate, which must be fully assembled & set. (again, can use typical loom sized wires)
Coil secondary windings (ie plug leads) to the correct spark plugs (as normal)
Starter motor lead (ie the +ve) can be loose and firmly pushed onto the batt +ve to crank… but expect heavy sparks if doing so. DON’T have neat petrol about. A better way could be to include the starter solenoid, ie connect the big battery +ve to one post (Heavy cable), the starter motor lead (+ve) to the other post (heavy cable), one small wire to the battery -ve, and leave the other small wire loose (loom sized cables will do). To crank, just touch this last small wire to the battery +ve.
Think that’s about it… again, there may be the odd spark… don’t have anything volatile / neat fuel around.