another option here. Check out the 'anodized gear' comments.
http://www.nissansilvia.com/fo...&st=0
the disc, pictured in that thread, coupled with a modified oe cam gear is all you need.
http://www.nissansilvia.com/fo...07379
I'd think they would be inexpensive & ez to machine.I recall a Z31 owner similarly modifying stock sohc vg30 gears and offering them to forum enthusiasts for ~$60 ea. a while back.
If not, maybe NST could do some for the ca18 like their 4AG piece.simple and looks good .....$150/pair. (only thing I'd change is move the adjuster bolts outward, closer towards the circumference)
http://www.nonstoptuning.com/pNSTcamGea ... mGears.htm