The attaching hardware for the radio delete cover/plate (pick a name) is documented in the 64-66 and 67-68 spreadsheets. The information came from the appropriate Mustang Assembly Manuals and matches the hardware information in Ford Car Parts (aka MPC, 75 edition) for 66 and 67, with 65 (and 64 by default) and 68 having no hardware referenced. The 1969 cover, C9ZB-6504302-N, is not referenced in the MPC (ref Body Sec 042, var pages).
Jim