Clutch Push Rod Length - ES2 Vertical G'Box / AMC Clutch

... so you'll need to measure it up. That's what I'd do even if it was standard as there's no telling what's been changed.

Easy enough - get a long piece of appropriate diameter rod and insert it from the gearbox end after removing the actuating scroll with the clutch in place. Push it up against the adjuster and you'll be able to mark off the correct length.

Someone please correct me if I'm wrong - but I think you'll find a 6mm rod in a 1/4"  (=6.35mm) hole is required.  Harden and temper the tips.

Just checked one in a doll's head box.  It has 6mm rod, but a 1/4" rod is an easy sliding fit.  I considered changing to 1/4" to reduce oil migration along the rod.  Not done so yet, but from what you write it's been done by others.