What does it actually take to put reverse on a SD motor?

I've got a 40hp efi that I'm thinking of adding reverse to and does anyone sell/manufacture the parts and then I can assemble? I've got friends with all the cnc/laser/machine tooling but not sure what is really needed or if someone makes it I'd just buy it and do any mods necessary after that. A parts list out there?

Thanks

An 89.00 short shaft trolling motor on the stern works for me
if the water is too deep for the push pole.....

Always wondered why no one fabbed a trolling motor to the SD
or transom the way the airboat guys do theirs....