Which piston size is compatible with my car?

[Balsaeed]

I have a 1969 280SL
Engine number 130983-12-005851

Which piston size is compatible with my car ? Because i came to an understanding that it depends on the engine number and when it was manufactured

[Pawel66]

For 130983-12-005851 I see:

Up to engine 983 10/50 004596 983 12/52 007229

A 130 030 95 17 PISTON STANDARD 86.5 MM
or
A 130 030 98 17 PISTON STANDARD 86,5 MM (check availability)

then

A 130 030 75 17 PISTON INTERMEDIATE SIZE 86.75 MM (check availability)

then

A 130 030 96 17 PISTON REPAIR SIZE I 87 MM (NLA)
or
A 130 030 99 17 TLOK REPAIR SIZE I 87 MM

then

A 130 030 00 18 TLOK REPAIR SIZE II 87.5 MM

then

A 130 030 83 17 PISTON REPAIR SIZE III (NLA)

[Cees Klumper]

As Pawel notes, there are various sizes that correspond to different stages of rebuilding/repair of the engine. In order to really know what pistons you need, you have to inspect the current pistons and cylinder bores, and go from there. Unless you are 100% certain the block has never been opened - but even then your best bet is to inspect it.