GMAC Financial Services is among the smallest of the seven bailout recipients under Kenneth Feinberg's purview. But the 22,700-person firm was not small enough to escape Mr. Feinberg's cuts. The Detroit-based auto financier for General Motors and Chrysler dealerships and the operator of the online Ally Bank initially proposed that it compensate top executives with a split of 20% cash and 80% stock. Mr. Feinberg pushed cash levels down so the cash-stock percentage mix now stands at about 15-85, according to people familiar with the situation.

It is expected overall compensation for GMAC's top 25 will drop by about 50% as a result of Mr. Feinberg's final ruling, said a person close to the process.

With the exception of a few executives, the top 25 at GMAC will make no more than $500,000 in base salary, said people familiar with the process. The same measure also is being applying to other firms.