Trump Place's commercial parcel.

What's better than 1.7 million square feet of elusive commercial something? Why thousands of cash-creating apartments, of course.

As Donald J. Trump explores running for president, he's also running numbers on developing Trump Place's commercial parcel as apartments.

The 1970's plan to develop 18.5 million square feet on the 74 acres of Penn Yards was whittled and sawed down to 7.9 million square feet, consisting of a 21-acre park, 16 apartment buildings containing 5,700 units, plus 110,000 square feet of service-commercial and a 1.69 million square-foot commercial parcel.

The latter "superblock," running from 59th to 61st streets and West End Avenue to Riverside Boulevard, has dogged developer Trump and his Hong Kong partners, just like Larry Silverstein's 42nd Street block of 1 million square feet of "something" tormented him - until he got in the ground with River Place's first tower this year.

Trump lost NBC for his tallest-building in the world Television City tower in 1988, and last year nearly snared CBS for a new studio building before Cost Cutter Mel Karmazin decided it was cheaper to retrofit. Thence came studio tours for East and West Coast shoppers.

Meanwhile, Brodsky's Manhattan West triumphantly ended the decade's residential hiatus; Tishman Speyer bought from ABC and is completing its West End Avenue 500ish apartments; Joseph Korff's River Center is close to reality; the Ginsbergs are designing; Macklowe has a site reserved; and Trump Place's two residential towers are filling. The last of the 516 rentals was leased - ironically - to a relative of Trump's Veep Abe Wallach, and has a waiting list; and the 377-unit condo is 70 percent sold at prices averaging $710 a foot. Those profits are actually funding the construction of the next Trump Place building, currently in the ground.

"There is a lot of residential going on," said Wallach of the Upper West Side construction spree.

Last week, Trump confided to Silverstein's NYU Real Estate Institute class that he's looking at turning the superblock into super apartments.

So far, he's talked with "David Childs, Hugh Hardy and other great architects," he said, and is discussing the change with City Planning.

No matter what is built, the morsel has to go through the Uniform Land Use Review Process, which means the community gets a swipe, too.

"We have to do a lot of cost-benefit analysis," says Wallach, before any final decision is made.

Apartment marketer Andrew Heiberger of Citi-Habitats, who does not represent Trump, thinks the developer and his partners will make more money on residential. "It's a C-plus office location," he says, but the Manhattan apartment market "is crazy," with less than a 1 percent vacancy rate for new product." But Heiberger says Trump will have to watch his unit mix and have many more studio, and one-bedrooms because that superblock, with views overlooking the McKim end & White-designed steam plant, is less of a family neighborhood. At $50 a foot, Heiberger says Trump will rent out, "No problem."

But with a construction schedule of approximately two to four buildings coming on line each year, it could be a decade before Trump Place is complete. So in the next few years west end will become very hot.

"It's an emerging area and someday an office building might make sense there, but apartments would rent up as fast as you can build them," agrees Wallach.