Here's an another idea you could think about. Get a nice soft top. I'm sure someone makes one fairly close to the tops for 1st gen 4runner's. A hard cap would just be wsy to heavy off road. Then get an accordion boot. They are actually made to work together with a hard cap were you remove the rear sliding window and it connects to both truck and cap. But Im sure you could make something work with the soft top. Maybe build some sort of ply wood bulk head to attach the boot and create a weather proof seal. Just throwing out options, I know how tough it is to need the extra room but you already have a good starting platform with your truck now
Sent from my SPH-L520 using Tapatalk