The gearbox is still stock. Cause of the great torque, mostly I start with the 2nd gear, from 20 to 30 mph I use the 4rd, and then the 6th. There is allways enough acceleration, but of course, to have fun, I use the other gears, too. But on the highway is normaly no need to change gears.
The engine swap was performed by a small shop, which has a lot experience in mechanical and electronical upgrading MB vehicles.
Here is some more information. Unfortunately only in german. They did a realy good job including the offical approval by an engineer, without that you get no change from a car in germany street legal.