I'll sell you my 1998 7.3 E-350 EB SMB 2wd with 98k miles for $25,000.00. The floor plan is similar to this. You can have Chris at Ujoint 4x4 it from 12-22k depending on if you do the conversion yourself or have his shop do it...http://www.ujointoffroad.com/
That is about the cheapest...
Loved following your build - very thoughtful rig, inspired my own purchase of a 4Runner Trail. These rigs can be a great example of "less is more"...took mine over Imogene pass between Telluride and Ouray bone stock, the only people annoyed with me were dick heads in Jeeps with snarky attitudes...
I don't worry about a fuel additive but I do care about a coolant additive. Before I bought my 7.3, all my Ford Head buddies made sure to tell me about cavitation and what you need to do to protect the cylinders. Here is a quick snippet from another forum. Tons of stuff on the web you...
For anyone interested, I just had these put on my 5th gen 4Runner last week at Slee. I may be the first customer and their website is not updated yet, but they do have a 5th gen with KDSS kit now. http://www.sleeoffroad.com/products/4runner_sliders.htm
Love the truck, just wish it was the double cab...I'm leaning toward setting up a rig like this but haven't made my final decision...http://www.fourwh.com/product/fleet-flat-bed-popup-truck-camper-tray-tacoma/
I'll let you know