[1985 CCX]

Here is my two cents

1) Use small spacers between aluminum and the glass footbox to creat an air gap. (1/8")
2) Use 1/8" rivets with 1/2" - 5/8" reach
3) 1/8" Locking rings on the inside of box as it will help with securing them.
4) Aluminum rivets are ok as you are only contacting glass and aluminum. When connecting steel to glass use SS rivets as dissimilar metals will not hold out.
5) Original cars only had glass, I have seen some asbestos insulation however I would not go that route.

Have fun!