I have seen Transpartswearhouse before, located in Redding, Ca. They did have 2 or 3 listed last time I looked there.
HMMM...maybe a road trip up there? Might need a pass port or something to enter ****** land....
Might cost as much in fuel as the part.
Do some research, there is a deeper sump for the GV, think it adds another qt of ATF. Then as i read, they recommend to change the fluid every 5 - 6K miles.
here is their web site
https://www.gearvendors.com/index.html
Here is a YT Vid I saved where the guy installed a Cummins in a chevy and the GV, pretty clean set up.
17 min video, shows how to shift it manually etc...
at the end show the under carriage how it is mounted.
Of course your van and auto trans will probably shift different. Think I read where you use a Head light dimmer switch on the floor to shift it.
Here is some info on installing it on a van. from genscriptor
www.nickpisca.com
Goat