1973 Mack R685RST - Christchurch Truck Show. The Mack R Model Was A Class 8 Heavy-duty Truck First Introduced In The Early 1960s By Mack Trucks, To Replace The Very Successful Mack B Model.[1] Its Production Ran For 40 Years Until The RD Model Was Discontinued In 2002 And The RB And DM Models Were Discontinued In 2005. The First R Models Introduced Were Powered By Mack Thermodyne Diesel And Gasoline Engines. In 1973 The R Cab Was Given A Makeover To Include A Deeper Rear Wall For More Room And A New Dashboard Design. Photo