a common upgrade for the a15 is a 79mm (80thou over) mazda flatop piston, i have these in my race coupe. but dont know about the a14 bore size.
as for stroking maybe offset grinding the crank. ive worked to do both of those to an a15 would take it out to 1734ccs but thats only a theory. check the wiki im sure that there is something in there.
cheers kurt