Lost reverse on 65 dart gt

Running it without hooking up the throttle pressure linkage (what you called the kickdown) is extremely detrimental to a torqueflite. Without it hooked up it'll generally cook a transmission pretty fast. What ever you do get it hooked up BEFORE YOU DRIVE IT AGAIN. Since you say you have all forward gears my guess is the issue at hand is in the shift cable or adjustment. Sorry, I don't know where to buy one. Hopefully someone will chime in on where to get one. Running it with the throttle pressure linkage unhooked has probably made for some quick wear on the bands so while your replacing the cable adjust the bands and maybe you'll get lucky and it'll work ok again.