Where to source new connector for turn signal/ignition switches

You shouldn't have to cut any wires. I haven't fooled with those 1974 connectors, but I haven't seen any connector which doesn't have a way to release the pins from the plastic housing. Re parts, I have found vintage terminals in Dodge motorhomes a few decades later, like ones for my 1965 in a 1980's motorhome. Looks like they were using up surplus parts or just didn't update the design.