Looking For LED lights for my 68 Barracuda
…and another thing: many of our cars' turn signals are invisible from a side view, but that's not hard to fix so the front side markers (on all '68 and '70-up cars) do double-duty as side markers
and side turn signal flashers. See
here for info. This is a very good safety improvement; your turn signals become visible to the side (cars in the next lane, bicyclists, pedestrians) instead of just front- or rear-on. It is also fully road-legal.
There are two methods described at the link. With one-wire side marker lights ('68) the logic module method is the way to go. With two-wire side marker lights ('70-up) you can use either of the two methods. If you want the side markers always to flash in phase with the front and rear indicators, use the module method. If you don't want to buy a module and don't mind the side markers flashing in opposite-phase with the front/rear blinkers when your headlamps are on, use the cross-feed method (no module required, just a couple of wire connectors). Either way is legal throughout North America; elsewhere in the world, international rules do not permit opposite-phase flashing because it's considered potentially confusing to an observer who can see both the front and the side flashers at the same time.
(You can also use the module method to convert your fender-top turn signal repeaters to combination marker/repeaters)