I have used several sets of Elepahant ears to mount B-RB and Hemis in 1967 and on A bodys, I have also used one of AndyF motor plate like you have to mount a blown Street Hemi in a 1971 Pro Street Cuda
I use a piece of 1 inch x 1/4 or 3/16 inch thick angle iron welded onto the top of the frame rails and drill and bolt a 3/8 allen head fastener to hold them together
My picture may not be real good as the motor is in the car the way I drive it, but here goes anyways
BTW, it is hard to get it behind the frame tab but that is the way I run it, higher and further back