Marchal lamp # 61243303 is not the original GT40 donor part fitting.
The captive screw tabs are in the wrong position on the reflector rim and need to be moved. Tricky job.
No idea how far off this is.
Based on a print that was included in gt40 uncovered but that might be off a std marchal backing and not the gt40 backing.
A couple of more tweaks until it is printable.
The original knob is 12P internal, think it needs to be a hex in order to print.
Printed on a bambu x1 carbon.