Hard shift to 2nd and 3rd

Sounds like someone has installed a shift improver kit in it. If you look at the linkage that hooks to the carb and runs down to the transmission you'll see an adjustable rod and socket where it connects at the carb. Shorten the linkage by screwing in the socket/rod assy. together and that'll lower the throttle pressure which in turn will soften the shift. Adjust it 1/2~1 turn at a time and test drive it each time until you get it where you like it. You'll notice that adjusting the throttle pressure rod shorter will also cause the shift points to be lowered and if you go too far you'll loose passing gear so you may just have to try and achieve a happy medium.

BTW: there is only 1 shift cable. It's the front one. The rear cable is the parking cable.