You need to adjust your throttle pressure linkage. Get it right or you can damage the trans.
For years I adjusted Mopar kickdowns with out a manual. If the shift is soon unhook the linkage from the carb stud and screw it in. If the photo you posted is your car, I would close the gap up by a half and test drive it. If it needs more, give it more. If it shifts too late, unscrew it and open up the gap in the slot. This isn't rocket science. I had a Coronet that didn't even have linkage. I wired the lever at the transmission for a medium shift and drove it that way daily. tmm