Need Ford O/D trans info

[55project]

I have an 86 Ford motorhome with a 460/ C-6 trans , still carb'ed motor. Not injected.
What O/D trans can i put inplace of the C-6 ? It will have to handle towing the car and enclosed trailer around. That's pretty much all we use it for.

And do i need any electrical/computer parts to make it work?
If so, do they sell the parts i need?

Thanks