65/66 Dart Tail Lamp Bulb?

You might also check out using a #67 in those taillights. Might be a hair too bright, but, the advantage to using them is that the bulb is shorter, so, it sits farther from the lens and won't melt/warp it on a long night drive. Might be worth a look. Just swap one from your license plate light to test out if you like it or not.