PLEASE help! 360 vs 273 oil pans different?

You are correct, the 65 SB oil pan is different than later years. It has a slight depression for the steering arm. As mentioned, you can't use your old 65 pan on your 360 because the rear bearing block is bigger. It would fit a 318 or 340 SB though. I think your only choice is to ding the oil pan as you plan.