If you got a bleedy great liquid marker pen , and put a hairline scribed across the piston crown & liner top lip , thatd give you a ' in line ' orientation on assembly , if its not already apart .
If yoyu wernt washing it or suchlike before fitting .
Id use a straight edge & knife tip , carefully .
A FLASHLIGHT with a good battery , into the Ex Port , would put some light on things . Normally a stain on the liner ,
so getting it centralised in the exhaust cut out / hole , should be effective .
Or give up & give the pieces to ME .