Here is an episode of 3 maps for Doom 2 including various difficulties. (Maps work with vanilla source ports but i recommend using ZDoom or equivalent)
Place Doom2.wad and 3HL.wad in the folder of your favorite source port or create an executable shortcut and enter a command line in the properties of the shortcut:
-iwad DOOM2.wad -file 3HL.wad .