I went out and tinkered for a minute last night.
Here is the engine mount slotted. The 4wd frame is 1/2" taller in the area that the engine cross member mounts. More bad news is where the front cross member that the brake proportioning valve mounts to is like 6" tall from the 4x4 but the 2wd frame rail is only about 5-1/4" tall in the area it should mount so that is going to be interesting as well...
I was installing my new U bolts and found some issues I need to resolve. Always something. I need a shorter stud for one.
Still need to find somewhere I can buy just 2 cheap U bolts that are square, for a 2.5" wide leaf spring and 13" long. These will temporarily mount the blocks until I can build my rear hangers. I need to be able to roll this thing out the shop soon to clean and paint the frame.