The rear driver's side trim panel will swap in fine. This way you don't end up with the GLS parcel shelf mounts.
Here is a GLS to Weekender before the panel was swapped. You can see the GLS shelf mounts on the left.
The front door panels will not swap. They look the same, but they are not.
The table needs the metal support bar and table leg mount to be cut free from the donor van.
The rear bed just hits bump stops and latches at the end of this rails to hold it in place.
You will need to drill holes for the new seat/bed rails and weld nuts to the underside of the chassis. This way the rails are secure and can be removed later by one person if needed. The spots for the holes are already punched in the floor.
You will need to make a wood subfloor for the bed to roll on easily. The wood floor from the donor van won't work. The 1993 door opening is a different size.(larger).
Here you can see a front MV/Weekender wood floor stripped of its top thin carpet layer. Notice the rear seat mounts out by the edges.
The rear section here still had the thick all carpet GLS flooring. You can see the seat mount cut outs for the GLS rear seat.
Just take out your existing carpet and use it as a pattern on some 1/4" plywood to make a wood subfloor. The CaveVan vinyl can then be glued down to that. I can leave all the seat mount holes uncut at the moment so that you can fine tune it to your floor and swap.
Good luck! Sounds like a fun project! Post pictures.
This van was a GLS to Weekender conversion FWIW