Here is a full level hack for Contra which adds a degree of challenge by adding more enemies & making levels harder to traverse but you are able to adjust how many lives you can start off with at the title screen.
Contra (USA).nes - NOINTRO
CRC32: C50A8304
MD5: 7BDAD8B4A7A56A634C9649D20BD3011B
SHA-1: C9EA66BB7CB30AD5343F1721B1D4D3219859319B
SHA-256: 26541A5550EE22DEEB3D5484E4A96130219B58CFF74D068FB1EB6567FA5E5519