Hello,
My '70 Challenger's rear speakers have been missing since I've owned the car. Now, I'd like to install a pair of 6"x9" speakers.

I have a package tray installed with speaker cutouts, but was wondering what type of fastener (metal screws or bolts?) is recommended to secure the speakers w/o puncturing through the package tray?

Thanks much for any info on how you guys have done this!

i took the package tray out and set the speakers through the hole, secured them from the top, then put the package tray over it. (you cannot see the speakers through the package tray)

Might be a little more disassembly then you hoped for, but the cleanest way to do it.

Before worrying about fasteners and screws..
You should check the height of the 6x9 speaker frame.
Often this can be higher than the pressed metal recess which can cause the package tray to be raised and not to sit down properly. Also if the speaker is a multi-driver such as a 2-way or 3-way again check the height of the mid/tweeter frame you do not want the package tray to rest directly on this or one can get vibrations..

In extreme cases we have mounted 6x9s from below the metal frame. Key point is you want the package tray to have some clearance between it and the speaker, or there will be vibrations and rattles..
Or even restricted speaker output.

Just my $0.02..

Factory speakers were installed from under the package tray with sheet metal screws.

If installing from underneath, what size sheet metal screws were used? Are there any other fasteners needed to hold these screws in place or do they grip onto the metal frame if the right size?

Thanks!

I fit in that way but using fasteners

What type of fastener is used for this ? Thanks!

I've used fasteners that look like small C nuts. you know.....the things the fender bolts tighten up into?