i thought that by law you had to have the same diameter wheels either side, like you could have 14's on the front and 15's on the back but you couldnt have a 14 on one side and a 15 on the other.
some drifty cars have lets say 17's on the front and 18's on the rear but that a rwd car, theres nothing stopping you doing this to a k10 though.
my shocks are knackered all round and i have a awfull ride, when i put the pulsar wheels on which are only 14's (but much wider than standard) i had to cut the whole lip off and bang the inner arch in a bit so it wouldnt rub inside. its great now, ive got worrn knackerd shocks, whells that are 7% larger circumfrence than stock and definatly a wider offset and it dosent rub at all, so when i sort it out lowered good shocks it will be ace.
id say on a micra for practical resons 15" is tops, definatly choose youre offset well and do go above a 7-10% larger circumfrence on youre wheels and watch out for the width of the wheel, you could be in my position where youre hitting the lip and the inner arch, i dont know what the pulsar wheels are 6 1/2j? if you go way wide you would have to get a offset that dosent hit the iner arch and get angela angle grinder out and cut the rear wheel arch off and get a set of overfenders and blend them on with sammy sander, a lot of work