I haven't installed a windshield washer bottle yet....
The wiring is all there to connect the low fluid level indicator and for the pump. I thought about getting a late 90's or 2001+ washer bottle to try mounting ahead of the driver's side battery - just like the new trucks, but didn't quite get there yet... I haven't driven it in the rain - much...
A 1994-98 APP electronic accelerator pedal will bolt right onto where your mechanical pedal is now. That's why I spent the time to see whether the 6.5 pedal assy would work (it's easier than fabricating in a GMT-800 pedal assy). The 6.5 pedal assy works well with just a couple wire swaps in the harness.
The cruise control is electronic, so yes, you'll not need any of the truck's original components - though you should save everything. Someone will need them here in TDP for a repair/retrofit using a 6.5.
Yes, I'd probably try adapting the new under-dash harness to the 90's dash.
I needed to relocate the trans crossmember primarily because I was replacing a TH700R4 with an Allison. The 4L80-E you have is longer - apparently about the same as an Allison. Has to be some luck in this...
Cutting the floor.... That's what I don't understand. I didn't need to, and I didn't use a body lift. What crossmember did you have to "get it over"? The transmission crossmember is easily removed for installation. The torsion bar crossmember stays in place during the R&R.
Sounds like progress!
Jim
PS: I'm moving this thread into the General Diesel forum.