USG Plaster CIty had six known diesels in their history (off the top of my head):
#1203 a "75 ton" C-C custom built by Porter, now stored serviceable at Sumpter Valley
#? a 45 ton siderod Whitcomb (There in 1953 working with SP #9 when the Porter was getting a new engine). P.A. Copeland believes it went to a USG related operation in Canada.
1303/1403 GE 54 ton units bought in 1956 now at Golden, CO property of GLRR, Inc.
#111, 112, 113 units built for the WP&Y but never delivered, #113 wrecked and scrapped for parts
Are you counting the Porter as the six axle unit?
US Potash in New Mexico had three of the "70 ton" C+C units (GE model designation C+C 140/140? 6GE747, weight might vary), #4 1948,#5 1952, #6 195?. Units scrapped/salvaged for parts within a few years of USP's end of rail operations.
Still looking for info on GE 50 tonners.
First order three units for Chiriqui Land Co. 8/52 s/n 1143-31146 #56-58; #56 re#803 scrapped in Alimirante 2007; #57-58 sold Bandegua (Guatemala) by 1967?
Second order for the Granada Co. in Dominican Republic 8/52 s/n 31146 #6; sold to Chiriqui Land Co. as their second #56; scrapped in Changuinola 2007. s/n 31147 might be a second unit, s/n 31148 is not (per Jay Reed)
Third order supposed to be for Dutch Guiana/Suriname per P.A. Copeland; built between 8/52 and 5/54, s/n should be between 31147 and 32189.