Contrary to what a lot people say,you can get all sorts of power rom the 450 engine...in the US you have the option of ringing Isky himself ,and I'll bet his son Ron has already ground a profile or two for mecedes Engines in the past.
If you want extra horses,PUT THE COLD AIR TUBE BACK ON!!! Mercedes have had this idea on their cars since 1959 with good reason! it WORKS!.
Any 6.9 owner wil tell that just installing a W126 560 air cleaner with the twin snorkles gives more power that you can actually feel.
make sure the engine is a high compression engine and not a low compression item from a W116 or even a W109.....
The intake is pretty small for a V8 and I think if twin throttle bodies were installed on the intake manifold a lot more horsepower would be unleashed.
The Kjet Injection air meter body could be swapped for a 560 intake,the fuel distributors are the same but the plate area is larger.
I still like the idea of fitting a larger engine and I have been assisting a guy to install a 6.9 into a W107...not at all easy actaully.AMG made a special crossmember,shifted the location of the oil filter ( 6.9's are different to 6.3's ) and made a diffrent hood to clear the engine.They even made a new injection system for the three cars they built with the 6.9 ( bored to 7.2....}:-) )
Heres one with a 6.3 ...
We have been discussing this swap for some time now here:
The guy I'm helping has spoken with the man at AMG ( Germany) who did all the work onthe W107 engine swaps ,so we are on the right track so far...
AMG still have lots of parts in stock,but you need to able to Quote part numbers befoe you will get a response.
The exhuast on the right can be made by any competant muffler shop...