TRQ. Another Chevy Tech here from the 60's till 90's. The rear disc brake was not an option in the Impala. I ordered mine in 1968 from the September factory order sheet and would have ordered the discs if they were available. The 11 inch drums are more than adequate to stop mine. I serviced the new cars also. A performance dealer could have done the work. The E-brake cables may have worked. NICK L72