65 Barracuda A 904LA trans. leakage problem

That cable leads to the park part of the transmission. FWIW the other cable goes to the R, N, D, 2, 1. At one time Imperial Services might have reproduced the cable but not sure now. If not then your only solution would be to find a good used one. There are 2 different cables - one for column shift and one for floor shift so if you do a WANTED ad, specify which you need. Good luck with your search!