Thank you everyone for the quick replies. I posted the same questions on several other "off road/overland/whatever-you-call-it" forums yesterday and have not received any replies, I feel incredibly welcomed here.
I am becoming quite aware that I have a lot to learn about my FJ as well.
For the heavier springs, are there any good ones that won't result in any lift? Everything that I have found causes lift and I am not sure I want that before I can justify purchasing new tires.
With regards to the transmission cooler, am I correct in assuming that it is something that wouldn't be done at a Toyota dealership?
On that note, if anyone on here knows a good off road vehicle mechanic in the greater Hillsboro, Oregon area I would appreciate that. The one that I worked with to have the front coilovers installed did a fine job as far as I can tell, but didn't exactly inspire me with the confidence to return for future visits.
Thank you for the fuel storage ideas. I went with the cheaper plastic tongue box to save money, as well as avoiding the rotopax mounts. Trying to cut costs wherever I can has limited my options a bit for extra fuel.
I am also not getting the roof rack installed on the trailer to save money, so that slumber jack tarp that hooks to the wheels looks great. An awning that connects to the FJ's roof rack would be nice but not fill the intended purpose of covering the galley while cooking. Here is a picture of the exact kitchen set up I will have for reference on what I am trying to cover:
Thank you all for your help thus far!