John,
I had owned from new both 1960 3000 4 seater (BT7) and 2 seaters (BN7). The hardtop came with the 4 seater. When this car was laid up long term do to an accident, I purchased a 2 seater. I was able to use the 4 seat hardtop on the 2 seater with simple drilling of relocated "J clamp" mounting holes on the hardtop. I used the hardtop many years this way. So, the factory hardtop for all 6 cylinder, side screened big Healeys can be fitted to cars '57 to '62.