I used plus nuts (similar to rivnuts but they are bigger and a bit stronger) for my build. The tool I used was this:
https://www.astrotools.com/product/13-plusnut-and-extra-long-rivet-nut-setter-kit-metric-sae/
Apparently this tool will also do rivnuts as well. You do not need this exact make and model, but look for something similar.
Also, you should use the right nut for the job. If it is not a structural item, rivnuts are fine. But if you are trying to tie down heavier items (like a cabinet) then you should consider using plus nuts. Same idea as rivnuts but they are stronger and have a higher pull-out rating. One thing to note, however, is that plus nuts can wind up spinning in the hole you drill (or in the existing hole of your van if you are using an existing hole). This is because the sheet metal is often too thin for it to properly grab onto. Once that happens, it is almost impossible to fix without getting a power file and grinding the metal plus nut down to nothing and pounding it out again (ask me how I know... sigh). So if you are putting these into your van I would add a washer to "thicken" the sheet metal they are attaching to. Basically get a washer with the same sized hole as the plus nut and put that between the head of the nut and the sheet metal. That fixed the spinning issue for me.
I don't think rivnuts are likely to have the same issue because they are rated for thinner sheet metal.
Here is a description of plus nuts vs. rivnuts: https://www.pointsunknown.com/blog/2016/10/lessons-learned-rivnuts-vs-plusnuts/
How to install plus nuts: https://www.google.com/search?q=how+to+install+plus+nuts&oq=how+to+install+plus+nuts&aqs=chrome..69i57j0i20i263i512j0i390l2.3095j0j4&sourceid=chrome&ie=UTF-8#kpvalbx=_bOw6YfO-Gp-d5OUPjoWN2As43
(Note, they are using a different tool. Trust me, if you are doing more than 4 or 5 it pays to get the more expensive tool I linked to above).
Finally, if you over-tighten the plus nuts (and I suspect this also applies to rivnuts) then you might crush the threads. This is not hard to fix. (start by not over-tightening the nuts... but this takes a few until you get the hang of it). If you crush the plus nut threads just get a tap (a tool used to cut threads) that matches your plus nut (usually named something like 1/4-20) and run it through the nut to "reset" the threads. It might sound complicated but it is super easy. Tap's can be found at any hardware store.
Good luck!