So this is a 14' boat with large diameter gear hauling tubes?
The biggest thing thats going to affect your decision is how wide to make the frame. Do you want 66" or 72" frame? You will probably need 72" to do a 120 qt cooler. With the wider frame and 10' oars this will impact your ability to float in tight spaces.
I've done the Rogue on a 14' nrs cat with 72" frame but you can run that river with an 18' boat
I have a 66" frame for local rivers. I can just squeeze a 120 qt cooler using the nrs drop rails pushed out. Normally i run a 94. If i had my say i'd have a 76" gear frame and 68" smaller cat frame. Seems like i see cheap used 44" wide dryboxes
Hey, if you want me to take a dump in a box and mark it "guaranteed", I will. I got spare time.