The vacuum guage approach works and I suspect existed before timing lights were available. Remember the timing light approach is no more accurate than the timing marks. The vacuum guage approach is based on what works best.
Standard automotive type stranded wire is correct.
Is the ignition switch up to the load a 10 guage wire will support? You need something to protect the switch and wire whether its a fuse, circuit breaker or fusable link.
My 78 year-old uncle would probably love working with your uncle.
