dude tolerances vary from each torrie, no one can rly say eg. 'any lower than 2.2156" and it will not clear speed humps'...seriously mate just take what PLEANTY of helpful people are saying to you onboard first, THINK about it, THEN post....there is some valuable pointers i think your missing re: lowering & re: spoilers +&- kit.
My UC looked just like yours (black grille and all [exept it is a factory torana]) but had hotwires and let me also say it would look ghay with just a rear spoiler.
Also take in what Nathan is saying (he has seen MANY UC's), flares = big wheels otherwise it also looks ghay. With that, don't bother with a front spoiler if you dont have flares, IMO it will look unfinished = also ghay.
Now what i think looks good and what anyone else thinks looks good is just preference but its much past that now, personally i think you've got more than enough feedback in this thread to make a decision in regards to flares &or spoilers.
OK now to explain your lowering situation again....
here mine is on STD springs (a loooonggg time ago)

ROUGHLY 1.25" (&5 yrs) later

As heath & I have said no lower with 13" rims or your exhaust will catch on everything.
Anyway, its your car, so you've gotta make the decisions, but you've racked up heaps of opinions (which is what you were after), so go and take it all in, figure out what you want from the car at this point in time THEN post us back, i don't know if its just me, but otherwise im finding that this is all beating around the bush a bit.
Either way enjoy im sure we'll see it at a cruise soon enough
Brad.