Transmission Main Shaft Nut 27mm or 30mm 4 and 5 speed 240Z 260Z 280Z

New OEM Nissan transmission mainshaft nut for 5-speed for Datsun 280Z and 280ZX.  Two options for this nut.  The M27 seems to be the more common size.

A:  M27-1.00 left hand thread nut.  Hex head is 38mm.  Nut I.D. is 26mm.

B:  M30-1.00 left hand thread nut.  Hex head is 38mm.  Nut I.D. is 29mm.

*note some transmissions might be RH and some LH thread.