A customer from Germany came to us to complete his dream car:  a W109 300SEL 6.3.

He had  just bought a much sought after W109-300SEL 6.3, but with an unique problem:  Its body was so rotten that he had no option that to buy another 300SEL but with 4.5 motorization.

So the project included to transplant everything from the rotten car to the pristine 300SEL 4.5 body .

Even when both cars share the same external appearance they have major differences on the wiring harnesses.  It is not possible to transplant the harness from the 6.3 directly without major modifications:

1. Increasing charging capacity.  
   Customer wanted to have an AC system on this car, therefore we had to enlarge the power handling of the system to met that goal
2. Revised Instrumentation
   Customer accepted our suggestion of having and electrically driven temperature gauge.  For that purpose a cluster coming from a W114, which has the same look, was bought, and we made the changes on the instrumentation harness branch to make everything work seamlessly.   The 6.3 Tachometer was placed in the position of the clock as anyone can imagine.
3. Accessories on the engine bay relocated
   Again 6.3 version differs a lot from 4.5.  Base harness coming from 4.5 car was heavily modified to eliminate the original D-Jetronic control logic and build in place the relay arrangement responsible of running the cold start logic.  The engine control harness on 6.3 is plugged at the middle of the firewall, so the necessary signals and connectors were brought there. Position of the alternator, an a/c compressor were changed accordingly to fit the 6.3 engine layout
   
4. New engine control harness
   The original 6.3 engine control harness was so deteriorated, that a new one from scratch was constructed.
   

This were among the most important changes that were developed to make this project a reality.  On the following link you may see the evolution of this work one step at a time.