awhile back there was a WTB thread which I lost track of - I promised to check my 914-6 GT car & post the findings - so here it is - I have a pair of the red plastic hellas with long horn tubes - see pic - have not been hooked up for years. They have bolts, so I guess they can be opened up and rebuilt. A battery test results in a low tone on one, and a grunt from the other. PM me if y'all are still lookin for em. Free if ya pay the shipping cost.
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"... I am German, and if it has no logic it's meaningless."
914 & 914-6 parts FS 03-2021 
www.tinyurl.com/2pmpmv8y
911 parts FS 2022
https://tinyurl.com/911-Parts-FS-LCM