go to 'rvlocksandmore'. they can help with locks, keys, etc. our cardinal also had different key for front and rear. I was able to take the locks off. they are only held on by 4 screws on the inside and a couple in the strike plate. once you get them off you will see a sticker with a key code. order a new lock with a key code that matches one of the ones you have and put things back together. now the locks will have the same key. a new lock was about $15. total time is maybe 45 minutes. also, there are only 50 different key codes in total.
2015 cardinal model 3825fl
2015 dodge ram 3500 dually