Looks like your gonna have to swap out your spindles:

1967 was the first year for disc brakes but they used dual piston calipers, 1968 was the last year of the dual piston caliper. 1969-74 all used the improved design single piston caliper. All disc brake conversions use the improved single piston caliper. These disc brake conversions will fit all the 64-72 GM A-body Cars. This includes: 64-72 GTO, Lemans, Tempest, Chevelle, Elcamino, Monte Carlo, Skylark, Grand Sport, Cutlass, 442, F-85. These sets will also fit all 67-69 F-body and 68-74 X-body cars. This includes Camaro, Firebird, Trans Am, Nova, Ventura - GTO, Appolo, Omega.