3/16" pop rivets do the job well unless the floor is shot. You can get rivets in aluminum, steel, and stainless steel. You can also get them with a closed end. For extra strength they even sell backing washers.
 
Dennis
 
> Date: Thu, 15 Aug 2013 08:34:41 -0700
> From: tom@CARCHRAE.NET
> Subject: how is the gas pedal affixed?
> To: vanagon@GERRY.VANAGON.COM
> 
> I was not having a good van day, and to top it off, when pulling out of the
> gas station, the accelerator pedal didn't work.  On inspection, the pedal
> had come loose from the floor.
> 
> The pedal looks like this:
> 
> http://a248.e.akamai.net/origin-cdn.volusion.com/o42db.t5sus/v/vspfiles/photos/VWC-251-721-511-D-2.jpg
> 
> On the floor, I found two metal pegs that poke into the two plastic holes
> on the end of the gas pedal.  However, I did not find anything else that
> would fix the pedal down.
> 
> I found this picture, indicating some kind of rivet
> http://i105.photobucket.com/albums/m218/tencentlife/van%20tech%20items/DSC01057.jpg
> 
> So, I guess I am looking for two large rivets?
> 
> I'm curious to know why I didn't find any rivets under the carpet -
> although there was a lot of crud under the carpet.  Perhaps someone just
> glued it in the past?...
> 
> Tom