As far as I know no one makes or has manufactured an upgraded heavyweight passenger car truck with roller bearings unless a brass model maybe of a Santa Fe car from Pecos River Brass had them. The six wheeled trucks under the Bachmann "Big Dome" car and the Kato El Cap Hi Level diner represent modern Budd prototypes, and the six wheel trucks under the Kato Union Pacific COLA train set baggage/ mail storage car is of a 1949-50 ACF prototype. How about a Shape Ways project? Nate Goodman (Nato). Salt Lake, Utah.