Morgan Stanley & Co., the New York investment banking firm, is attempting to organize a group of blue-chip investors to purchase all of Conrail's federally owned stock, then resell it to the public over a period of years.

If such a plan were to win government approval, Conrail's present management team would remain in control of the railroad and the Transportation Department's plan to sell Conrail to Norfolk Southern Corp. for $1.2 billion would go by the boards.

Conrail Chairman L. Stanley Crane is openly opposing the Norfolk Southern bid and told the New Jersey Chamber of Commerce Monday that the Morgan Stanley package will meet or exceed the Norfolk Southern offer.

Morgan Stanley has been reported close to announcing a package on several occasions, but financial sources said yesterday that the proposal is subject to amendment and that potential investors are in, then out, then in again.

Morgan Stanley officials declined comment, calling speculation about the proposal premature.

As a practical matter, however, there is a Friday deadline. Rep. John D. Dingell (D-Mich.), chairman of the House Energy and Commerce Committee, told Morgan Stanley at a recent hearing that if it is going to make an offer, it should be by that date.

The committee is considering legislation proposed by the Reagan administration that is needed before the Norfolk Southern deal can be closed.

Crane is clearly supporting the Morgan Stanley effort and has found a strange ally in CSX Corp., Norfolk Southern's major railroad rival east of the Mississippi.

CSX officials, who are vigorously lobbying against a Norfolk Southern-Conrail combine, have said they would commit up to $200 million to participate in the Morgan Stanley proposal. CSX is the largest railroad holding company in the East. But if Norfolk Southern succeeds in acquiring Conrail, it will take the lead.

There has been considerable speculation about investors other than CSX. The list is said to include other railroads, several utilities and various investment groups.

Morgan Stanley has acted as a consultant for Conrail management during the past year as the federal government considered various bidders. It is understood to be acting on its own in putting together this package.