HOW TO ADJUST 65 DART AUTO SHIFT CABLES?

Cudamark,
Looks like I have a sticking blocker valve. Book says above 20 mph, enough fluid pressure to move that valve and prevent putting car in reverse. Interestingly enough, my extra 65 904 transmission is missing that part. Can you lend any expertise? Wondering if a spring went astray and jammed it.
thanks
gene
Sorry Gene, I haven't run into that problem before, so, I don't have any advice on what to do.