[dmjlambert]

Does the right rear light flash OK with the right turn signal on?

First thing to check is the bulbs, make sure they actually work when you insert them in another socket or use test wires. Perhaps swap left to right.

See if you get different results for right front with the hazard flashers.

Check the wiring to see if it is in good shape. Some of the wires run inside the driver side fender where rats like to chew. Check it out.

Look for the under dash curved connector for steering column. Here are the wire colors for wires that go into under-dash harness:

purple - power from turn signal flasher
brown - power from hazard flasher
white - brake light power
black - horn button
light blue - left front turn signal light
dark blue - right front turn signal light
yellow - left rear turn signal/brake light
green - right rear turn signal/brake light

Use a test light probe or multimeter to check for expected voltages by inserting probe into the back of the connector while it is connected to the steering column.