Faced with an aging fleet that no longer suited its' needs the NSW Railways rebuilt some of their older 72'6" mainline passenger cars in the mid 1970's to a more modern design.

They removed the old style compartments and moved the centrally located passenger door to the end of the car to make a higher capacity car for interurban use.

Older style cars were converted from 1976 and some lasted in service until 1990 on the NSW network. 3 cars were lost in the 1977 Granville accident which necessitated renumbering of some cars and introduction of other cars.

Initially painted Deep Indian Red these cars were repainted to the new corporate Candy Stripe scheme from 1982 onwards.

All up 24 cars were converted to Supplementary Interurban use and the NSW Railways referred to them as collectively as MUB Cars.

SI-203c Candy Supplementary Interurban Cars