@ icerabbit, I have only taken out one bolt in the floor rails and one in the side rails. They both have a nut under the metal floor of the van. However, if you crawl under the van, what you find where you should see that nut is, instead, a longitudinal box beam running the length of the cargo floor. So, there is no way to fabricate that nut in there without either installing it before the frame is put together, doubtful because maintaining location tolerances to fit floor rails would be impossible, or installing it from above after the van steel subfloor is fabricated. I just looked again and I can see 3 more box beams below the steel subfloor with proper spacing to fit passenger van seat rails. One of those is above the gas tank, but the van steel floor is at the top of that beam 2" above the gas tank. No, there is no plywood floor below the L-track tie-down rail. The L-track is an inch tall and is slotted into the ply floor, which must exist below the 3/8" composition floor that I can readily see surrounding the L-tracks. The L-tracks are hefty aluminum, unlike the more normal 7/16" thick wall-mounted L-track. The floor rails are extruded with a horizontal rib at their midline, so, looking from the end, they are a figure 8 with square corners. Where they have mounting bolts tying them to the floor, that rib is drilled large enough for the head of the torx bolt to go through it. So, only the bottom of the L-track is bolted to the floor. That way, unlike with normal L-track, you can slide a clamp down the track without hitting a bolt head because the bolt heads are recessed in the lower chamber of the L-track. After looking again today, I would bet with 90% security that the cargo van can easily become a passenger van and be safe. By simply slotting the floor for the 2 inner seat tracks 21-1/4 apart to match the floor bolt mounting points, and using Mercedes or equivalent tracks, you can install a seat safely. The only thing missing will be the side curtain air bags, which don't work on a large number of cars today because of the giant recall! Nobody is going ape-sh... and parking their cars due to that recall. If you put a child in the middle of a tested rock-n-roll bed or an OEM Mercedes seat, I'm confident they will be as safe as in a passenger Metris, but you can be your own judge, assuming you, too, find mounting nuts when you slot your plywood to install the seat tracks as I believe you will. I prefer to live fact-based. Yes, I am speculating that what I have seen, when I looked at it in detail, is typical of the rest of the van floor. I guess whoever disassembles first will be the one to inform this community with the facts. Stay tuned. For the doubters, please read the Magnuson-Moss act of 1975. It is legal to modify your van without impacting the warranty unless something you do provably destroys the integrity of the vehicle. We are talking of doing no such thing. Also, icerabbit, I realise you are just replicating L-track, but others may be interested in going further.