As for numbers, .120 over on the 265 block is basically 283 cubic inches.
265 bore was 3.7495"-3.7525"
283 bore was 3.8745"-3.8775
Stroke was 3.0" on both.
When we were young bucks I remember being told on the SBC engines a good rule of thumb was you could figure on picking up approximately 5 and a half cubic inches for each .030 over they were bored. Using that, you'd take the 265 to 287, but it was just a guide and not exact.
