I've been running 6v positive ground in my '51 GMC for 32 years. Noooo problems. The biggest problem that I see in 6 volt systems is the use of 12 volt wires, which are roughly 1/2 the gauge they should be for a 6v system. Battery cables should be two ought (2/0) for 6 volt. That's a heavier gauge than 12 volt. Folks complain about slow cranking 6 volt systems but that is always a result of undersized cables.
