As demonstrated on the Tips page 1969/1970 Gauge and Interior Differences, there are significant differences in equipment between 1969 and 1970 Mustangs. The maplight and clock wiring is no exception. There are some vendors that now sell new clock harnesses but some of them are only applicable for 1969 cars although they may state that they are for 69 and 70. Below is a diagram that shows how to adapt a 69 clock harness to work with a 1970 wiring harness. This technique uses a standard 3 wire trailer pigtail that you can buy at any parts store. The end you need to use is the one with the 2 female and 1 male terminal. The lengths of the wires you use is up to how you install everything.