I'm pretty sure A14 and A15 rods are the same.
Its just the piston thats different.
Be careful taking meat off the crown of the piston as you might run out of compression height and blow holes in the tops of the pistons.
You may need to cut reliefs in the top of the block for valve clearance if you go with bigger ones......I did. This might limit where your top ring also sits on your piston depending on the depth of them.
This and the valve relief cuts will depend on the size of the camshaft you use.
Measure the size of the chambers after the valves are fitted to calculate comp ratio.
Mine runs essentially flat top pistons....24cc chambers. I calculate it at approx 12.9:1 but my slide rule might be off.
1mm overbore A15 crank (stroke)

Neil