If the St. Louis Cardinals football team moves to Baltimore, the first order of business ought to be a trade with the Indianapolis Colts.

Bill Bidwill, owner of the Cardinals, should call Robert Irsay, owner of the Colts, and offer to trade names.

Such a deal not only makes sense but would help both teams make money. That ought to get the collective Bidwill-Ersay attention.

The deal makes sense because the Colts belong to Baltimore and the Cardinals belong, if not to Chicago or St. Louis, at least to the Midwest.

The football Cardinals were founded in Chicago in 1921 and didn't move to St. Louis until 1960. An identity now in Indianapolis would mean that throughout the team's history it never strayed more than 300 miles from ''home.'' Pro football fans in places like Springfield, Decatur and Danville, Ill., who backed the Chicago Cardinals and then the St. Louis Cardinals, would find it easy to switch allegiance to the Indianapolis Cardinals. At least easier than switching allegiance to an out-of-state team with an East Coast identity.

Bob Irsay himself is from Chicago. Would he not be more comfortable owning ''the old Chicago Cardinals'' than the embarrassingly misnomered Indianapolis Colts? Surely in the long run he would be more affluent. Many diehard Cardinals fans in St. Louis and southern Illinois would remain Cardinals fans. St. Louis, which clearly has a thing about Cardinals, is a little over 200 miles from Indianapolis.

Irsay could even go one better. The state bird of Indiana is the Cardinal. Why not a regional team? Why not the Indiana Cardinals? It even sounds better than Indianapolis Colts.

For Bidwill, the advantages of owning the Colts in Baltimore are just as apparent. All the money that would otherwise be spent introducing the team and converting Colts fans to Cardinal fans could go instead for football talent. Make the Colts a winning team, in a new stadium, and by 1992 Bidwill might just be proud owner of the most valuable franchise in the NFL.

What's in a name? Image, logos, trademarks, fan loyalty and a bit of football history. Clearly the Colts' name is worth more in Baltimore and the Cardinals' name is worth more in Indianapolis. These guys should get together.

Curt Matthews