[72malibu]

Figured I'd update my progress so far in case anybody is trying to do something similar. See photos of updated design and the factory speaker setup below.

I received the new kick panels from USA1 Industries. They are dyed in the 73-74 dark saddle color that matches the 75 Gentleman Jim interior.

I needed to resize my original design for the grilles somewhat. I'm going with a 6-7/8" diameter. That's right where the radius of the kick panels stops. I shortened the air holes so that you won't see the kick panel behind the grill, just the black speaker cone.

The 6" pin cushion 8-10 ohm speakers from Turnswitch/SMElectro-Tech are a perfect fit - the frame is a little under 7" diameter and the cone is a perfect fit to the opening of the kick panels. I will be mounting the speaker to the back of the kick panel and the grill on top. I think I'm going to use 8-32 or M4 countersunk screws/nuts instead of standoff studs to hold everything together.