im no p plater and havnt been for quite some time but isnt the law only saying that you cant drive v8s and turbo cars it doesnt say anything about engine transplants... but i could be wrong. i would recomend talking to qld transport and getting the correct advice and not listening to hear say. i would recomend reading what dd has given you and try using the search feature, as many poeple havedone this conversion. in qld the a15 would have to be mod plated anyway so dont forget the engineering costs, where as if you use a a14 you dont need engineering.

again check the wiki and search button for strut swaps there is heaps of info, everything from 120y stanza standard with silvia brakes s13 ect ect

dont use blocks as they are illegal in qld for a few $$ more you may aswell get the leafs reset cost about $160 for both sides. plus it looks cleaner.

the power of the a12 can be quite high for such a small engine but the key factor is money, as it seems you are quite young and as i remember i didnt have much of that. i would stick with the a14 extractors exhaust and a nice carby.

have fun