Al, the 165/15's fit just fine on a 4.5 rim and since that was (one of) the stock Porsche size rims and since they'd be lighter than the 5.5's, it just made sense to go that way.
I have to add that I'm very impressed with the quality of the Vintage 190's. The guys didn't even need weights on the wheels/tires, they were that balanced.
The castings are impeccable. I chose the polished for the vintage/stock look and the hubcap clips held on the rims with stainless panhead/allen bolts into perfectly threaded holes, cad-plated round-nose lug nuts, lug bolts that easily installed using the supplied allen wrench, these wheels are as nice (and light) as Technomagnesio except I can purchase a set of 4 190's for the price of one Techno.
Whitecloud told me she feels like the prom queen wearing these shoes.