70 Duster rear speaker size?

I used kicker 6x9s in the rear. I had to bolt them from the botto side in the trunk so theu would fit under the package tray. My new package tray had holes in it for dual speakers.

I bought a bracket from a member on here a few years back. It mounts two 4 or 4.5 inch speakers in the factoy location in the dash. Used kicker speakers all around powered by a retrosound radio. It's good enough for me