rear brake cylinders cabriolet 86 auto

hi.
  just changing both rear brake slave cylinders on my 86 cabriolet auto out and have come across the usual fun. the old ones are lucas 1007 types with a large 14mm diameter piston end with a deep shoulder for the end of the brake shoe to sit on.. the ones from the local autofactor are 1007 type but have 10mm diameter ends with a very shallow shoulder..will the new type be fine or do i need to search for VW original ATE or lockhheed types. many thanks.