Ditto on McMaster-Carr......
I used a 5-lb hammer and a sharpened screwdriver. Don't knock the heads off on the aluminum side, make sure that you cut the heads off of the steel side, so you won't gouge the panels. A lot of the rivets will come on out, but some, you'll have to use a punch and drive the shafts out of 'em.
You could use all pop-rivets.... while some spots have to have pops just because you can't get to the opposing side, earlier trucks did use normal rivets.... later trucks used mostly pops, instead, though, so don't think that you "have" to use normal rivets (unless you're wanting to really do it back to original). You'll have to have a pop rivet gun anyway, so, you could do all pops, but... If you do use normal rivets in addition to pop rivets, to do 'em well you'll need a buck of some sort, and a drive tool in a air-hammer... I would not recommend trying to do 'em w/o an air compressor.... (but as w/ anything Rover, you could if you really wanted....)
Good luck...
-L