The R129 Mercedes-Benz SL class comes with some good Bose speakers and AMP. I decided to start the upgrade process with the door woofers. The stock ones are 1 Ohm and there is almost nothing on the market with that resistance. Based on other retrofits I opted to go with a 2 Ohm woofer. The system I bought is the JBL GTO608C. It comes with separate woofers and tweeters.
To avoid cutting wires an adapter was used.
The fit was perfect in depth and diameter.