Major changes are being proposed in Southborough’s local government, and residents are invited to hear about them all tomorrow at a special public meeting. The Drafting Committee for Town Manager Legislation has suggested residents consider expanding the Board of Selectmen from three to five members, and shifting to a town manager system, instead of the current town administrator position. The committee has said that having three, part-time volunteer selectmen manage the town’s $46 million budget and day-to-day operations is no longer practical. The committee will detail its findings during the meeting starting at 7 p.m. tomorrow in Cordaville Hall, 9 Cordaville Road. The committee’s report is available at Town Hall, the Southborough Library, and online through a link at www.southboroughtown.com.