yes,i've done that.i've managed to get both 96 & 106 main jets from a15 carbs.maybe just go to a nissan dealer & inquire about new jets,or take a walk round a wreckers,checking the datsuns.try a 96 main to start,then go to the 106 if necessary.also,try to find bigger idle jets at the same time.you can also get bigger secondaries from the same carbs,i think i got 140's,150's & 160's from various raids.