Good morning! IMHO 60 deg. difference from fire box end to other end is quite a bit for a RF pit.
Did u use any of the calculators to figure out your fire box to cook chamber opening, air inlet to fire box, stack size and height? If the FB to CC opening is not correct, to small, then the air flow in the pit could be to restricted causing the extra heat at the FB end. Same with wrong size air inlet or stack size.
If the above is not the case and you are not happy with that much differance end to end you may want to install a heat shield plate below your RF plate here is a picture that Dave Omak drew up for someone else with the same problem.
All of that said some people like to have different temps thru there pit to allow for cooking different meats at he same time.
Good luck with your pit!!