Your location isn't listed, so I can't comment on what's legal in your area. But to answer your question, I would not use any glues in the joints. With all the vibration and movement, it's entirely probable that the bonds might not hold, and where they do may chunk off wood that's glued. If the joints are secured with bolts, washers, and nuts, that, IMO is sufficient.
In the 70s I removed a pickup bed from a 3/4 ton Chevy and configured an 8' x 10' flatbed based only on the two main chassis members. On the overall grid of 4x4s and laminated 2x4s, my first bed was T&G #2 SYP. That bed lasted over 10 years. When I finally replaced it I used 3/4" marine grade plywood, which went for another 10 years. I went through more engines and transmissions than truck beds.
I'm still using a 4'x8' flatbed trailer, that started out in life as a 4'x4' tire carrier trailer used at race tracks. I made a wood frame and it became a 4'x8' trailer, and I added a sheet of marine grade plywood. It sits outside and has been used periodically since 1991.
The truck would pass state inspections (when our State had them). As for the trailer, there's no inspections for 'homemade'.