pop rivets for a transmission hump?

You could also use sheet metal screws, that's what I did with the 4 speed hump in my Duster. Much easier to deal with shift linkage adjustments and transmission installs with the hump out of the car.

And you don't need all that many, all that Ma Mopar did was some spot welds and seam sealer. And there weren't that many spot welds on the originals to begin with.