Valtek Lifepod is my go to versatile vehicle storage personally. Can be secured to a seat rail and fits under the seat. Plus is water resistant being a huge advantage to most options.
In my ram I have a lockrdown console vault which is pretty indestructible but pricey.
Several options would do...
35x12.50 on stock wheels no issues here and the tire shop had no issue mounting and balancing them. Have about 3k miles on them so far. Again same as above it is a mojave so wider axle helps some.
Ran some 37x13.50s on a 8" wide rim no issues for years on a 2500. Put all kinds of miles on it...
Installed some desertdoesit short seat jackets. Man night and day difference it made in comfort for driving. Only took about 20 minutes to do both sides and well worth the cost they are well made.