In 1870-72, John Marius Wilson's Imperial Gazetteer of England and Wales described Powerstock like this:
POORSTOCK, a village and a parish in Beaminster district, Dorset. The village stands on an affluent of the river Brit, near the Brid port railway, 4 miles N E of Brid port; was once a market-town; and has a station on the railway, and a post-office under Brid port. The parish includes the tythings of West Milton, Mappercombe, Nettlescombe, South Poorton, Witherston, and part of Loscombe; and is a liberty. ...
Acres, 4,078. Rated property, £4, 639. Pop., 1,067. Houses, 229. The property is subdivided. The living is a vicarage, united with the chapelry of West Milton, in the diocese of Salisbury. Value, £195.* Patrons, the Dean and Chapter of Salisbury. The church was rebuilt in 1866, at a cost of more than £15,000; is in the style of the 14th and 15thcenturies; and consists of nave, aisles, transept, chancel, and porch, with a tower 106 feet high. There is a parochial school.
GB Historical GIS / University of Portsmouth, History of Powerstock in West Dorset | Map and description, A Vision of Britain through Time.
Date accessed: 30th March 2017
Click here for more detailed advice on finding places within A Vision of Britain through Time , and maybe some references to other places called " Powerstock ".