Jimmie,
Although I am now also considering using the EPAS; my first thought was the Toyota box. I have not done either yet. I want to see someone else's install of an EPAS under the dash of an AD truck.
Just food for thought, the Toy box works well with a GM pump, from what I read. Also backed up by the fact that if you buy an upgrade kit for your FJ, the kit comes with a GM pump. They say the pressures make the box work better than the Toy pump.
https://www.dropbox.com/s/rerghxemrlog7fa/ebay%20fj40%20kit_4_s-l1600.jpg?dl=0https://www.dropbox.com/s/b16nkwm0f2hftxn/FJ40%20PS%20Kit%201%2040psknobox.jpg?dl=0The issue I foresee, at least on my 1 ton dually, would be the length and the shape of the pitman arm needed. Consider this need first. There is a flat pitman arm made for Toyota trucks, but it is about 3/4" shorter than the stock Toyota arm even. At least on a 1 ton, it needs to be quite long.
I also considered mounting the box inside the frame with the pitman shaft coming out through the side of the frame. This would shorten the length of the pitman needed.
https://www.dropbox.com/s/wmnp280a2ceurxc/Toyota%20PS%20in%20Stock%20Location..jpg?dl=0That being said, I bought my push pull box by posting a wanted ad on Pirate4x4.com. I think I ended up paying like $100.00 or $125 shipped. This is a 4x4 part; go where the 4x4 fans go. There is a Toyota section there in addition to a parts wanted and parts needed section. Ebay is way too high.
Also make sure you get the right box. There is a slight difference in the mounting angle that I didn't immediately notice.
https://www.dropbox.com/s/mumummv7y7k7zxo/129250066_3aa73bfcf7.jpg?dl=0 That might be an advantage, depending on your mounting angles. I think one is an FJ40 or 60 box and the other is the 79-84(85???) pickup or LC box, pre IFS at any rate. Mine came off of a Land Cruiser I think.
The EPAS is cheap and shouldn't require changing anything from the steering box down.
Larry W.
