Hope this hasn't been already asked and if so I could not find it.

As I am moving every 6-8 months to a new state I bought a trailer (now thats a bit too small or I have to much stuff).
Truck: 2004 V6 4runner 4wd SR5 with weight carrying hitch.

I have a 5x8 single axle enclosed trailer (trailer empty=997lbs as I recall) which was pulled from just south of San Jose Ca to Tucson Az with no problem (I don't expect one with Toyota).

What is the largest trailer I could comfortably tow with?
Can I replace the Weight carrying hitch with a Weight distributing hitch? (Which I plan on doing)
What is the best Transmission cooler to install?

I want a 6x10 or a 6x12 tandem axle but do not know if the 6x12 is a good idea nor how much it weighs.

Thank you,

Unfortunately a newbie....

 

You have a Class III hitch max weight of trailer plus cargo is 6K lbs with 600 lbs tongue weight

Try reading your owner's manual and searching online for weights of trailers you are considering but with more trailer weight you are going to be able to actually have less weight for cargo so it will be a trade off.