What choose a reverse valve body?

The reason is to avoid the possibility of hitting neutral or reverse. If you want a good RMVB go with cope's. I have one in two of my cars, love them. Another benefit is low band apply which helps protect the sprag clutch. Not all rmvb have low band apply so read the details.
https://www.coperacingtrans.com/?product=crt-727-904-pro-street-reverse-manual-valve-body
I run the billet rear servo and 4.2 lever.
https://www.coperacingtrans.com/?product=727-billet-aluminum-lowrev-servo-67up
https://www.coperacingtrans.com/?product=4-2-lever