Both the 48 and 50mm piston and cylinder will fit that saw.
The standard 038 AV had 48mm piston.
The 038AV super had a 50mm piston and the 038 Magnum had a 52mm piston. All with corresponding bore sizes.
I have the AV super but I read somewhere on here that its possible to put the piston and cylinder off the Magnum (which is the same as the MS380 I think) onto the smaller ones. Pretty sure you have to elongate the cylinder stud holes in order to fit it on though.