I've done a 3.8L conversion on a 190E so I know that will drop in to your 300CE. The 3.8L puts out about 218bhp and 225lb/ft of torque. This is about the same specs as a 3.2L or a 24v 3.0L so not really worth it for you I would think. Its a good, fast revving motor but if you have access to the 4.2L and 5.0L, I would go with those especially for the bigger chassis 124 cars. E-mail me your contact for the front clips. I have been interested in doing a 6.0L conversion in my coupe.
mvischer@cox.net
Thanks- Mike