Minnesota Public Radio announced yesterday that it's selling its for-profit catalog company to the Dayton Hudson corporation for 120 million dollars. About 90 million dollars in proceeds from the sale are expected to go into MPR's endowment... which would make it the largest in all of public broadcasting. Tom Thomas is with the Station Resource Group, an Washington D.C.-based organization of public radio stations from around the country. He says endowments are a relatively new development in public radio.