4.07 bore production 1974 block. 4.25 BPE crankshaft. Very little work to block to get it to swing full circle. A notch in the bottom of each cylinder and a little work on the pick-up tube. Pistons were supposed to be 4.06" but Wiseco made both sets I ordered at the same time 4.07", one set was for a .03 O.S. 340 block. Block was super thick so I went ahead and used the 4.07 pistons. Would of never went .06 except formula for 440 S.B. is 4.25 x 4.06