Nov 2 (Reuters) - Japan’s Seven & i Holdings Co Ltd , parent of the 7-Eleven convenience store chain, is aiming to sell as many as 300 gas stations following its deal to acquire Marathon Petroleum Corp for $21 billion, according to people familiar with the matter. Seven & i is working with investment bank Nomura Holdings Inc to solicit buyers, the sources said. Seven & i said in August it expected net proceeds of $1 billion, without disclosing how many stations it would sell. TDR Capital, the private equity firm that owns British petrol station operator EG Group and lost out to Seven & i in the race for Speedway, plans to make an offer for the gas stations, according to one of the sources. Seven & i Holdings and TDR Capital did not respond to requests for comment. Nomura declined to comment. Seven & i inked a deal in August to purchase Speedway’s roughly 3,900 stores in 35 U.S. states, in a bid to shift focus beyond Japan where its stores and supermarkets face a shrinking population, slow economic growth and tough price competition. The deal would leave Seven & i with some overlap between 7-Eleven and Speedway stores, which it is seeking to address by divesting up to 300 gas stations. (Reporting by Joshua Franklin in Boston; Editing by Richard Chang)