The GRP rod is a 29.5 mm x 4.20 mm top yoke x .0499 bottom yoke with a 5 mm Crank pin . The Go rod wont work as the top yoke on it is 3.99 mm.

and im glad you asked the question ! cos i dug out my engine Cemetary Box .. ( where all the ones that didnt make it live ) And found a GRP, and in its box i found an original new 28-0600 ROD ! in the pics below im using a CNC machine setting pole to measure its dia. The pole set i have was given to me from a huge CNC machining / engineering company here in AUS back a few years ago when i was designing and making custom rods for Drag Racing and Off road applications .. , the poles are used to calibrate their CNC machines and are extremely accurate. The 5 mm pole will fit snugly in the new 28-0600 and the new 21-0600 but not in the original 28-0600 as pictured below.

Hoep this finally puts this one to rest


Cheers MM