Those are American Racing Torq Thrust II's in a 15X6 size. They are available new - though not directly from American Racing - I bought mine through an eBay auction from a reseller.

They have a cast center welded to an extruded rim and are quite light for the size. American Racing also sells a Torq Thrust D which is a one piece cast wheel with the spokes painted gray - but the slightly different offset of the II works better on a 544 (II is 3.375 in, D is 3.625 in). In particular the front suspension of the 544 (upper pivot) will interfere more with a wheel that extends any more to the inside. In addition the tie rod rides inside the rim - so you can't go smaller than 15 inches (and must have a fairly thin rim at that). American Racing also sells custom sized and offset Torq Thrust II's if you need something unusual.

The 15X6 size with 205/60/15 rubber fills the fenders perfectly - I had to do only the most minor 'rolling' of the lip inside each rear fender. The improvement in handling of the 205/60/15 Yokohama's vs. the stock sized 165R15 Firestones is immense!

An example of a reseller - although the auctions on eBay tend to have better prices (they flood a bunch of auctions out there so you really aren't bidfding against anyone for the wheels).
http://www.4autostuff.net/wheels/amerracing/vintage/torq_thrust_2.htm