DETROIT, Michigan - Fiat is considering a plan to hold a public stock offering after the company buys 100% of Chrysler.The plan to sell shares is of a combined company, according to a source, is among several options being evaluated by Sergio Marchionne, CEO of both automakers.A stock offering would raise much-needed money for new-vehicle research at both companies and could help Fiat ride out the economic downturn in Europe.Fiat now owns 58.5% of Chrysler but wants the remaining 41.5% from a health-care trust fund for union retirees. The two sides differ on price; a US court might have to rule.GOING PUBLIC?Fiat and Marchionne were appointed to manage Chrysler in 2009 by the US government which had thrown a financial lifebelt to a drowning Chrysler. Since then Fiat has raised its stake in a resurgent Chrysler and Marchionne wants to merge the companies to generate more cost savings from joint research, management and purchasing.Fiat SpA shares are now traded publicly on the Milan stock exchange while Chrysler is technically a private company with no publicly traded shares. Presumably Fiat shareholders would be offered a stake in the new company if they approve the merger.Merging the companies would give Fiat access to Chrysler's cash holdings. Fiat shares Chrysler's profits but can't use the Detroit automaker's money for its own operations. Without Chrysler, Fiat would have lost $1.41-billion in 2012. Chrysler had $11.6-billion in cash at the end of 2012.Marchionne has said Fiat has 10 billion euros ($13 billion) in cash that can be used to cope with a severe slowdown in European auto sales and buy the trust fund's stake in Chrysler.