Sounds like you mean just the engine is different? Does the car have rear wheel discs also? Does the engine block reveal inself it to be a 250 engine? I believe the 250 block/head are clearly labelled as such. There are cars I have learned with engines out of the SE.
Sounds like this car has an unknown history. I would not consider this engine swap an impairment at all, as ong as it's a Mercedes engine suited to the chassis in good shape, compression, appearance of sparking plugs, running, correct IP. But be sure to inspect closely for other liberties/deviations that would not be good. There are many trim components in particular that you likely want to be of the 230 style.