Hy tobin1959, welcome, yes the two oil pans should bolt to the same block, be it a 235 or 261. That being said the two pans you have may not be interchangeable for your application, chassis constraints, oil pump pickup locations, oil capacities, may be different. If you want to change the pan to the good one you have, you must make sure it will work in your chassis, and the oil pump pickup will end up in the new pans sump, and allow the pan to bolt up to the block, good luck, hope that helps.