I'm finally going to be able to get my old chevy on the road again. I've gotten a free rebuildable 250, I believe from a later '70s model truck. One of the first things I noticed is that the engine mount pads on the engine block are different. The passenger side looks to be the same as original, but the bolt hole spacing is different. The driver side mount is quite different. The three bolt holes are not only spaced different, like the other side, but also the single bolt hole at the top is about an inch or so lower(meaning not flush) with the two lower bolt holes. I just want to know what's the deal with this? Many of the other inlines and v8s I've looked at seem to be interchangeable, why would this engine be different? Sorry this is so long. Thanks!