its simple if you want a straight forward answer and want to stay nissan, oterwise options are endless

low budget $90-3000
a-14 or a-15
a-14 provides higher revs/ a-15 more tourqe
what do you want it for, i guess if your gonna use the tray to carry something heavy some tourque would be good

$3000-6000
a14 or a15 with all the mods and go fast bits aswell as a straight as body fresh paint big mags loud stezza

higher budget $6000-15000
ca18det maybe sr20det (lot harder arguably no better)

above $15000
would you really want a 1200 worth that
try checking out some skylines preffreable save some more cookies and get GTR

p.s. i said as low as $90 cause i picked up an a-14 block at the wreckers for that and arguably i could bolt that in for nothing, not including gaskets and oil though