Re: flasher indicator unit
I had the flashers go dicky (not great when I got the car) on 74 midget and found them to be the two-wire rectangular tin cans. Inside found to be bimetallic - going back to pre-GCSE physics, the current passing through causes part to heat up and bend as different metals expand at different rates, breaking the contact, then cooling and remaking contact.
Anyway, mine were grotty and vacillating. I tried a couple of 'electronic' ones from a certain online source - actually turned out to be a solenoid-type relay with capacitor strapped across. They are soundly built and work well. They power via the current in-line between battery, lamp and earth.
Note that the flash rate is consequently dependent on nature of load, so if you were to fit say LEDs or different power lamps, or had poor connections then flashing will be dim, weak and try to flutter. A good earth connection is worth the effort - clean metal and silicone grease (not silicone rubber compound, although that would seal the connection...)