Someone can chime in if I am incorrect, but as I understand it, Stroke only changes with rod length and crank radius, see below;
For the same rod length as a stock sr20, your stroke won't change if you use a z32 piston. Only issue would be if the distance from wrist pin center to top of piston is larger than the Sr20 piston dimensions, you may run out of room and make contact with the valves and/or head.
You would have to know how much room youd have, with the piston at TDC, between the top of the piston and the surface of the head and/or valves at their respective positions.
If the z32 piston has the same dimension from wrist pin center to top of piston, then the only benefit would be a increase in piston diameter (bore) and a potential for a different ring land design.
Hope this helps somewhat.