That's a clue I have to take with a grain of salt because I successfully swapped a 603.96 in place of a bent rods 603.97. I'm no Einstein, the long blocks are externally identical! The only part of the swap that wasn't plug-n-play was converting the .97 turbo from vacuum wastegate to pressure wastegate. Doing so reduces the job of EDS to controlling idle speed, and even that is optional since a 603 can sustain idle without electricity. Then I totalled the car

Having owned an S420 prior to the 300SD 3.0, the difference the longer wheelbase provides is worth several weekends to me. Now that I drive an 87 300D, I know I want a bigger car. The bigger the better. And I like MB Diesels. I had an M103 for a few years. I'm happy those years are behind me. I'm not interested in an M104. I like the OM603. I understand what it says to me and it takes my abuse in stride

Another fellow did the more complicated 606 into 140 swap. Keeping the 603.97 IP, which is plug-n-play, keeps the swap sane. There is mechanical work fitting the intercooler but I hear the 140 engine bay is accommodating.

I'm confident I can get the engine installed and running. I'm concerned the car's electronics, particularly ABS and SRS, will reject the transplant. I'm also concerned California won't let me register the Frankenstein.

I appreciate your concern

Sixto
87 300D