All you really need is a wheel speed sense count that the trans computer is expecting.

The 97 gets wheel speed fed to the ABS computer ( bolted to the engine computer in under hood box ) then sends it over the CAN bus to the trans and engine computers. As you said, making the computers think there are still in the E will make this work. If you don't send a wheel speed the computer is expecting, the trans will go into limp and give a gear ratio fault.

There are a few ways to do this. Attach a wheel speed sensor to an electronic speedo ratio adjuster then feed the ABS what it is expecting.

Put a speed sensor on the drive shaft ( some MB have a speed sensor on the differential pinion ) then use the electronic speedo ratio adjuster and feed the signal to the ABS.

With both of these, there is a chance you can adjust tone wheel tooth count to get what you want without the speedo adjuster.

The trans computer should be under the front passenger floor, pull the carpet back and unbolt the floor pan. ( It is there on the C and SL so I'd expect the E top be the same. )

The only other real item you need to make the engine run is the antenna around the ignition lock , key that matches the DAS box and DAS box that matches the engine computer. The DAS box is behind the instrument cluster , left side above the peddle box.