Starting in 1910, wooden passengers cars were phased out in favor of all-steel "heavyweight" passenger cars. These heavier cars required more robust trucks, and the GSC Commonwealth six-wheel passenger truck was a common solution. These trucks were produced in at least two different variants ("drop-equalized" and "top-equalized").
Friction bearing trucks in the "drop-equalized" style are available from Micro-Trains and Rivarossi (the latter found on Atlas and Con-Cor heavyweight passenger cars) -
Micro-Trains based their 70' heavyweight baggage car on an Erie prototype. The trucks used under said cars were of the Commonwealth "straight top-equalized" ilk -
Rivarossi wheel diameter 0.194" (scale 31")
Rivarossi wheelbase between outer axles 0.774" (scale 10' 2")