328 Speaker question

The small dash speakers are fixed by 2 small bolts/nuts under the dash that you can approach without removing the dash, see below pics. The circular black cover is just clamped by 3 or 4 pins that you have access to when the speakers are removed.
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Hi, great info! I am interested in upgrading the factory tweeters in the dash any chance you have the dimensions of the factory units? Also looking to find the maximum depth for the door speakers?