Well those are new. Back when I was doing mine all I could find were tubular mounts or use the 67 and up BB mounts. Here is my build.
http://www.67-72chevytrucks.com/vboa...=259536&page=2 By the looks of those mounts, it seems you don't have to notch the frame at all. You can always call the vendor you bought them from and get more info from them. Another way is to just mock up the engine and see how it fits. I had my engine in and out about 20 times putting mine together.