There are supposedly at least 6 of the ST-tugboats (of the 327 design which is about 81 feet long) still on the lakes:

SUSAN L. of Selvick Marine Towing.   Built 1944 in Louisiana as a)ST-709, renamed b) STANLEY, c) SUSAN L. 

ALAN K. LUEDTKE of Luedtke Engineering.  Built 1944 in Louisiana as a) ST-527, renamed b)TWO RIVERS, c) ALAN K. LUEDTKE

FORNEY of the US Army Corps of Engineers. Built 1944 in Louisiana as a) ST-707, renamed b) FORNEY

OLD MISSION of Kindra Lake Towing.  Built 1944 in Sturgeon Bay, WI as a)

ST-880, renamed b) AVONDALE, c) ARDIENNE B., d)OLD MISSSION.  Supposedly has a retractable pilot house, so its appearance may be drastically changed.

KATHY LYNN of Ryba Marine Construction.  Built 1944 in Alabama, as a) ST-693, renamed b) SEA ISLANDER, c) KATHY LYNN

WILLIAM C. SELVICK of Selvick Marine Towing.  Built 1944 in Texas as a) ST-500 renamed b) SHERMAN H. SERRE, c) WILLIAM C. SELVICK

Sources:  Wayne Tug Database by Carl Wayne, Know Your Ships 2001