I'm a little surprised that since you were buying new pistons, that you would go for such a small size.
The standard A12A used 75mm pistons for 1237cc but you would need the A12A rods as these are the right length but have the larger wrist pin hole that all standard pistons above 73mm used.
The A12A rods are available in the US but not here in Australia, so you should be able to source them without too much drama.

Go for the A14 pistons at 76mm & you have the standard A13 spec which yeilds 1270cc.
The A12A rods would also be needed to make it work but all of these pistons share the same deck height.

The 1200 & later A12 cylinder blocks should handle this bore size without difficulty & I ran my 1200 GX engine with 'first oversize' A14 pistons' [76.5mm] for years. [1287cc]

All of this is inside the 1300cc limit for race class purposes but reduces the disadvantage of those engines that are closer to 1300.

It also makes for a very peppy 1200 GX

standard a12 bore is 73mm
u can use a14 pistons but u need differnt rods as the pin bore diamiter is different i think uc mazda pistons 77mm are the ones to go for as there flat top but in the precision auto parts catoluge is seez that the a10 piston are the same bore size as a12 but there dome top
(edit) dident see the a afer a12
yes you are right a12a or a13 used the 75mm pistons