The reason I suggested to mount them in the stock headlight buckets is that you don't have to worry about the height then...
I can't comment much on the legal height in the US, but here in Europe, that only seems to count for a manufacturer (so double check your rules about street legality)
I've seen quite a few 911s here with 935 conversions, which have the headlights in the front bumper and all are streetlegal here
Those even pass the TüV in Germany (and the German TüV is really anal about things)
You could also check for the Hella 90mm round units which are around $80 each IIRC (I'd be surprised if the Yukon headlights are much cheaper)
I'm still undecided myself...
I may go for round VW Rabbit headlights at the foglight location (cheap and simple)
Those NSX headlights sure look nice, but I'm sure they'll cost you an arm and a leg (or one of AAron's kidneys
)