Stanley Grassman comes with 3 spawn points for you to choose. Each file is responsible for different location:

brook_s2_stream0.wpl - Beachgate, opposite Faustin's house
manhat06_stream0.wpl - Middle Park, behind The Libertonian
nj_01_stream15.wpl - Westdyke, at the back of one of the houses

If you're on base IV, use the files from "IV" folder. If you're on DLCs, use the files from either TLAD or TBoGT folders. If you're on The Actual Complete Edition mod, use the files from TBoGT folder.

To install Beachgate location, replace "brook_s2_stream0.wpl" inside \pc\data\maps\east\brook_s2.img with the one provided
To install Middle Park location, replace "manhat06_stream0.wpl" inside \pc\data\maps\manhat\manhat06.img with the one provided
To install Westdyke location, replace "nj_01_stream15.wpl" inside \pc\data\maps\jersey\nj_01.img with the one provided

There is a provided map which pinpoints all 3 locations.