There is a shift kit change for the shifter out that makes it into a manual shifter like they advertise for the imports with the shifter on the shift lever. Much like the chebby shifter for when you put it in manual and use the little levers to shift. I think its by BPD out of phoenix, plugs into the OBD port. Dont know if it will work on the older trans but is supposed to give access to ALL the gears in the transmission.
Actually its BD diesel out of canada. Here is a link to the unit for a 6.0 ford diesel, cotact them they may have something for you?
https://www.dieselperformance.com/shop/product/1031369-tapshifter-exhaust-brake-ford-2003-2007-6-0l-f250-f350-powerstroke-595