: There is some concern for your safety which we should address. I have some alternatives for you to consider before you jump up to a true angle grinder. But all these types of tools, whether big or small, require eye protection, gloves and at least a long sleeve shirt because whatever tool you use, you will be using it to remove metal from those rivets. And an tool that removes metal will be flinging little shards of cut metal away from the tool. Here are some easier tools to consider beginning with:
: Per JWA's suggestion below, if you have an electric drill and are familiar with its use, then by all means, buy some new bits and try that first. )
1. Dremmel 395 (basically a mini die grinder)
2. Rotozip (a heavier duty version of the Dremmel)
Either of the foregoing tools would be a good introduction to removing metal and the salesperson at Home Depot or wherever can help you pick out the appropriate bits for your job.
3. Grinder (I prefer an angle grinder, and I burn out all H.F. grinders and even 4" Makita grinders, that is why I prefer the 4.5" Makita grinder)
This is the angle grinder I recommend. It is the safest because it has a paddle switch. And the first wheel which you see in the video is the one I personally would recommend you use on those rivets.
The video starts with this warning: "Power Tools are Fun but Dangerous. Use Them at Your Own Risk."
Take that warning to heart.
Ok, now for some realism. Are you sure you want to home build your own conversion van? If so, the project you are embarking on will require power tools. Either used by you or someone you pay to do the work for or with you. If you can't find someone competent to work with you it would be best to take some tool classes at Home Depot or the local community college to get familiar with their various uses and their safe use.
Yes, I have drilled out rivets and it certainly can be done, but as your drill bit dulls you may be tempted to put more pressure on the drill, making it more likely to slip off the rivet, push through the plastic wall and into the sheet metal wall of your van leaving a dent in the exterior. Also, IMO, there is probably no more scary tool around a vehicle than a drill. Because drills are designed to penetrate. So you better be very sure of what is on the other side (brake lines, fuel lines, airconditioning lines, electrical wiring, etc.) before you put a drill to a vehicle. (I mean kowing what is on the other side of the metal you are drilling and then measuring and marking and re-measuring at least five times before you put a drill to a vehicle.)
All three tools I mentioned above are primarily intended to work on the surface of the metal, not to penetrate like a drill.
Now for a little philosophy. I personally find a tool which has more power to be more controllable because I can apply only a little muscle pressure to make it do its work. A relatively powerful tool with a delicate hand where the hand merely guides the tool rather than pressuring the tool is best in my experience.
But the most important tool is patience.
In response to a recent window regulator write up on ford-trucks.com I actually got a rep from a guy who "liked your tool list." My tool list read as follows:
Tools to use:
: What I like about you, is that you actually stopped, posted pictures, and posed questions about how to proceed instead of bull in a china store rushing ahead. That patience is the most important tool you will ever own
Along with patience you need an unrelenting concern for safety. There is a 7.3L engine guru on ford-trucks.com named Christof13T who is an operator of computer and hand controlled metal machining equipment. He better than anybody knows not to rely on just safety glasses but goggles and full face mask (in fact I am going to edit my earlier post to include a full face mask). He had eye surgery a couple of weeks ago because a shard of metal he was grinding stuck in his eye. So be forewarned. Safety should never sleep.
Along with patience and safety, you must be open to learning how to see. You must see everything as it is, know what your tool can do (this knowledge is only acquired by practice on scrap metal), imagination for what the metal will look like as the tool is doing its work, and a realistic goal for what it will look like when you are done.
Again the reality is, that the project you've said you want to embark on will require power tools used by you or someone else.
But the most important tools you must own are patience, safety and learning how to see.