He will want to swap the diff too otherwise he will get poor mileage and the motor noise on the highway will be too much.

On the flywheels, the witness marks on my 280e were so faint as to be nearly invisible. I suggest marking the FW before taking it off the engine, then checking for balance. If both are neutral you are good. If one is not neutral the new FW for that engine needs to be match balanced to the fw which came from the factory on the engine you are using.

Most Fw are neutral but the results of a non neutral engine getting a neutral fw will be disasterous so best to check.

Good luck!

I am getting ready to do a 3 liter turbo swap into an 82 240d myself right now.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.