There are a few different ways to do a V8 CIS Benz.

1. Single Fogger Nozzle.
advantage= easy to install
disadvantage= Poor power/fuel distribution

2. Direct Port - 1 n2o nozzle and 1 fuel nozzle per port.
The best but time consuming to install.

3. Spray bar (long story)
advantage= easy to install

all of these you will have to take fuel from before the CIS Fuel Distributor. I use a regulator to drop the Fuel pressure down.
on the single fogger you can run a small gas jet off of the High Pressure fuel pump. Just make sure you don't exceed the max HP of the fuel pump. I think the 450SL was almost 300 hp. If you run a separate fuel pump it will have to be installed in the rear of the car and a 5/16" or 3/8" steel line brought forward.