The massive health-care trust fund to be established under the contract agreement between General Motors Corp. and the United Auto Workers presents an opportunity for investment advisers and money managers totaling upward of $66 billion should Ford Motor Co. and Chrysler LLC follow suit.

That pile of cash from the three companies, if managed as one fund, would rank among the 40 largest pension funds in the country, according to consulting firm Watson Wyatt Worldwide, bringing in tens of millions of dollars in fees to its managers. It would be nearly twice as large as the Harvard University endowment, the nation's largest college endowment.

"There's a potential for money managers to get new, large pools of money," said Cara Jareb, director of retiree medical consulting for Watson Wyatt.

But beyond the auto industry, there are few other big funds coming down the road, industry officials said. The trust -- known as a voluntary employees' beneficiary association, or VEBA -- makes sense mostly for companies fitting a relatively narrow profile: those with both unions and big retiree-health-care obligations. "It's hard to see a huge shift in companies doing exactly this kind of thing," said Derek Guyton, a partner at Mercer Consulting Group, a unit of Marsh & McLennan Cos.

Managing the one or more trusts that could emerge from Detroit's restructuring could be tricky. The GM VEBA is expected to operate much like a pension, with investments tailored to meeting an obligation to workers decades down the road. However, the returns on this trust will have to outpace those of a traditional pension to match the trajectory of health-care costs, which have been rising about 10% each year -- much faster than the overall rate of inflation.

In addition, much depends on what health-care costs do in the future. Many companies base their forecasts on a significant slowing in the rate of health-care inflation within the next five years, industry experts said. If that doesn't happen, it will be hard for the trusts to meet their obligations.

Before Wall Street can get its hands on a new VEBA, the agreement needs to be ratified by the union, which has nearly 74,000 members. That process is expected to start in earnest today, when UAW President Ron Gettelfinger is expected to meet with local union leaders from GM factories and review details of the proposed four-year contract.

Shares of both GM and Ford fell, as investors took profit from a postpact surge and as the focus shifted to whether Detroit can take advantage of the lifted liability to make up ground against its Asian competitors. In 4 p.m. New York Stock Exchange composite trading, GM shares fell $1.18, or 3.1%, to $36.46, while Ford was off 2.8%, or 25 cents, to $8.63, also on the Big Board.

VEBAs themselves aren't new. They have been around for decades. A VEBA is a trust fund in which money is set aside to pay for retiree benefits. The tax code gives special treatment to VEBAs set up as part of collective-bargaining agreements with unions.

At GM, the proposed contract allows the auto maker to take $51 billion in liabilities for UAW retiree health care and shift it to the VEBA. That trust will be funded over the next few years at about 70 cents on the dollar for those liabilities, said people familiar with the matter. The contributions by GM are expected to be predominantly in cash but also GM stock, including the possibility of convertible- preferred shares, these people said. GM will backstop the VEBA with an added $1.5 billion to $2 billion if health-care inflation exceeds projections, said two people briefed on the talks.

It will be many months before the trust is up and running, and before that can happen, it needs the go-ahead from a federal court to amend an existing health-care agreement from 2005. A similar arrangement worked out last year between the United Steelworkers and Goodyear Tire & Rubber Co. has been tied up in court. Once the GM VEBA is up and running, the trust will be managed much like a pension with a mix of bonds and stocks.

Similar arrangements are likely with Ford and Chrysler, which have an additional $40 billion or so in retiree health-care obligations to meet.

With so much money up for grabs, Wall Street is paying attention. "There are hundreds of guys out there circling, making calls, trying to get in the door with the UAW," said a person familiar with the matter. Compensation for advisers and money managers would vary based on composition of the final fund or funds; consultants and money managers usually get a percentage of assets and, in some cases, a cut of the profits.

A UAW spokesman didn't return calls seeking comment.

Utilities, defense companies and government contractors have been using VEBAs for decades. Following a 2004 accounting rule that changed how state and local governments treat their health-care obligations, many of those are shifting to VEBA trusts that operate like 401(k) plans with a menu of mutual funds. The VEBA for Washington state public employees includes funds from Vanguard Group and Pacific Investment Management Co. Another VEBA offering is Emeriti Retirement Health Solutions, a benefits plan designed for higher education. Two- year-old Emeriti offers participants a lineup of Fidelity mutual funds from which to choose.

Dallas L. Salisbury, head of the Employee Benefit Research Institute, a nonprofit research organization in Washington, D.C., said the primary candidates to adopt such a plan "are a relatively small remaining population."

The big question is whether any of these plans will provide the kinds of returns needed to keep up with health-care inflation. As big as the numbers are that companies use to predict their future obligations, some worry their models are too optimistic. Many start off using a 10% health-care inflation rate but drop that rate to about 5% within five years.

GM said in its latest annual report that it assumes health-care costs would rise by 9%, declining to 5% over six years. Being off by one percentage point would change its retiree-medical obligations by about $6 billion as of year-end 2006.