tom,hi i'm paul.the a15 valve sizes are from a gregory's for the 120y,which also lists a13's,a14's & A15's.so if i can't trust the gregory's that doesn't surprise me.as for pictures of my 1000 & the 1200's,the scanner is here,i just need learnin up on how to use it.also have the video of me rolling my 1200 at huntley colliery hillclimb,so one day i might figure out how to download that.wayne,as for the gearbox theory,that was past on to me from someone in south aus who made close ratio gearsets for the 1200 boxes.as i personally blown up both 1200 & 120y boxes,i much prefer the a14 sizes.surprisingly,yes,the only a12 box that seemed to last was a 120y 4 speed,but this was in front of an a12,not an a15 like the previous ones.the theory was the needle roller in the 120y box was a limitation.