speedometer needle goes nuts on 65 Cuda

If its the original one it's most likely the cable. Make sure it is not kinked at severe angle anywhere then try pulling the cable out & cleaning it, adding some lube and putting back in. If that does'nt work go with new cable. It is usually the cable having probs. before speedo bites the dust & they are the cheaper fix to start with.

Oldschoolcuda