Ronnie, it was not always 280SL on the block. If you look through the forum (Search), there is a table that describes what symbols were stamped and when (SE, SL SL/SE etc.). But it may be a true SL engine. If it has no number stamped - yes, may be a replacement engine. Some of those had a plate below number field with "Tauschaggregat" information. But perhaps not all.
As for the gearbox - the number you provided is a spare part number. I could not find it in the EPC, it does not recognize it. Maybe it is present somewhere on old paper parts lists. The "usual spare part number for gearbox in Pagoda was A1132700901. As it starts with 113, it is Pagoda related. Without a type plate that normally is on the gear box it may be difficult to say which one is it exactly. How many screws fixing the oil pan do you have? 16? Or 4? Try to look at the Technical Manual - there is a lot of info on engines and gear boxes, you may get the clues.
