2 Investors Join Goldman Sachs Landmark Bid : Real estate: Fiat, Greek shipping magnate will each buy 20% stakes in buyout plan for Rockefeller Center.

The family that controls Italian auto maker Fiat and a Greek shipping magnate have joined a group led by the investment firm Goldman, Sachs & Co. in its bid for Rockefeller Center.

Their money leaves investors David Rockefeller and New York real estate developer Tishman Speyer Properties putting up just 10% of the overall buyout funds, according to a filing Thursday with the Securities and Exchange Commission. Goldman will put in half.

The development is the most recent in the complex and sometimes contentious battle to win control of the Manhattan building complex, which has been mired in bankruptcy since May.

Besides the Goldman group, two others have made proposals for the Art Deco landmark.

Goldman--along with its Whitehall Street investment fund, Tishman and David Rockefeller--had proposed buying the center’s publicly traded mortgage holder for $7.75 a share, or $297 million.

On Tuesday, the group said it had discovered additional liabilities and would have to lower its bid. But it did not suggest a new price, saying instead it would need to meet with the mortgage holder, Rockefeller Center Properties Inc.

The group’s original proposal had envisioned the assumption of $800 million in liabilities.

In the SEC filing Thursday, the Goldman group not only disclosed that two new investors had come aboard but also spelled out the stake each party would have in the overall investment.

* Goldman and Whitehall will invest $220 million, or 50% of the total funds.

* Exor Group, a company controlled by the Agnelli family, which controls Fiat, will put in $90 million. That comes to 20% of the overall investment.

* Troutlet Investments Corp., controlled by Greek shipping magnate Stavros Niarchos, will also put in $90 million for a 20% stake.

* David Rockefeller, whose father built the property, will invest $20 million for a 5% stake.

* Tishman Speyer will also invest $20 million for a 5% stake.

The Exor and Troutlet investments do not change the size of the Goldman group’s bankroll. What they put in, the government filing said, makes up a part of a total of $220 million that David Rockefeller and Tishman Speyer had initially committed to make.

In addition to buying the mortgage holder, funds put in by the Goldman group would be used to buy out Rockefeller Center Properties convertible securities that are held by Goldman and Whitehall as well as for operating funds to run the center.

Rockefeller Center Properties is slated to take ownership of the 12-building complex from the center’s Japanese-controlled owners, according to a deal announced Sept. 12.

The oldest of the three active proposals for the center comes from a group that includes Chicago investor Sam Zell, General Electric Co. and Walt Disney Co.

Zell’s investors, the only group to have an agreement with the mortgage holder, last week proposed sweetening its $250-million offer to let existing shareholders retain a bigger stake. It also said it would consider buying Rockefeller Center Properties outright.

The investment fund Gotham Partners has made a proposal for the center that would leave existing shareholders in complete control.