well ill break it down for you, hopefully this will help.
the geo prizm is essentially a toyota corolla. any 1.6l, or 1.8l toyota sohc engine will work, but remember that you have to change the ecm if it is a different size as long as it's the same year. the tranny should also bolt up the same. there are no swap kits for it so dont think you can throw a 350 into it, but try looking at an engine swap for the same year corolla and you can use that. mazda is owned by ford, and geo is owned by chevy so the tranny is definitely not mazda, it's toyota. actually the only thing that is not toyota made for this car is the body and the dash board. thats about it. everything down the the struts, and seats can be interchanged within the same year up to 94. the 95s are in fact different but some interchanges can be made. the best thing you can do though is call a junk yard and ask to look into their
Hollander manual, which is pretty much a reference of any and every interchangable part for any car. well hope that helps 