try this!
Overbore the A12, fit the A14 pistons to give 1270cc. You'll have to use the A14 gudgeons, and bore the little end out in the rod. I think you skim the top of the pistons too..hmmm???
Skim an oval port head down until you get around 10.5:1 compression. You can take heaps off these...
Plonk in a 280 degree cam, use 32mm chokes in the 42's and shout it headers and a decent exhaust.
It'll make around 100hp at 7000rpm and be the most fun you can have with your pants on!
People wont believe it's not an A14!