VENOMUS

Your rear turnsignals are okay They are setup the same as in my '97 Cobra: the outboard two are parking lights(low bright) and brake/turnsignal/emergency flasher lights (high bright) by employing dual-element bulbs, while the inboard position's upper section is used as a parking light (low bright) only and the bottom section is your backup light. The outboard two bulbs have three wires to them (ground, low bright and high bright) while the inboard bulbs each have only two wires.
I designed and installed my own sequential rear turnsignals. I knew I had to change things about the inboard parking light to make it into the first on in the sequence, and was surprised to find that it actually had a dual-element (low bright and high bright) bulb in it. I carefully examined the socket itself and found that with some care I could drill a small hole in the rear of the socket and screw in a self-tapping screw such that it contacted the proper connection within the socket that when powered by a wire added as part of my sequential turnsignal circuit design, the high bright element of the bulb would light. I bought all of the necessary electrical parts (perf board, relays and capacitors) at Radio Shack for about thirty dollars.