Locking front M725 doors

Hello,

Has anyone found a way to add locking mechanism to the front doors of the M725? The only one I've ever seen is in the video I found on YouTube where he used 1980's Ford f250 panels and parts. Too bad he didn't get to explain how it was done. I spotted about 10 other cool mods he had made to his M725. Maybe if we ask the interviewer nicely, maybe hr will do a more in-depth interview. Here's the linkhttps://youtu.be/JeNzBzBbyAM

My 725 came with locking doors. It’s controlled by the inside doorhandles. Fully rotate in the direction opposite that opens door to lock from inside. Then exit out back door which should have key lock.

Wow...I have heard there was a way to do that but never had a clue how it worked...thanks for the info!!