RE: Webra Speed .12?
George,
Yup, you're right on the three K&B Conquests all having the same cylinder part number. I found my .15 book tonight and it appears that although Cox had two distinct liners for their RC and FF/Speed engines, K&B settled for just one for all three of their offerings. Don't know where I got the idea there were three separate cylinder liners.
Looks like the only difference was a choice of RC Carb or two venturis, standard finned head with std glo plug or the button type glohead. There was also a choice between spinner or standard prop nut and mini pipe or muffler.