I installed a 76 block using the Schumacker mounts in my 69 Cuda FB. But I installed the bare block with oil pump attached into the car first to check fitment of everything. I also ended up with less than 1/4 inch of web after cutting out for the oil pump maybe 3/16" or 5/32", and even had to take a corner off from the pressure relief valve cap nut. I centered the engine mount studs in the K slots, leveled the block left to right and snugged a nut on the studs. Then I attached an empty transmission case (easier to handle) to the block with 2 bolts and then installed the transmission mount and crossmember. It all fit perfectly doing it that way. The transmission mount has long slots in it on the tailshaft housing ears which allows for about an inch of fore and aft locating of the engine/transmission assembly. Your photo shows the engine mount stud to be off from the K slot center by just about the length of the transmission mount slots. Or maybe you have the transmission mount in backwards? There's no photo of that.
Another possibility, however far fetched, is that you might have a tailshaft housing on your TF that came from a later model van or truck which are slightly different in dimension and shape in several ways as compared to the old car parts Schumacker tooled up for. I got caught in that trap myself a couple of years back on a simple rebuild where the customer supplied the TF core and kit. The TF went together just fine but he couldn't bolt it into his 68 notchback because the tailshaft housing was from a late 80's B200 13 passenger van, luckily that was easy to swap out. The photo of your left engine mount shows it to be assembled correct except for the 3/8 bolt you've got in that lower bracket hole, all 3 bolts should be 7/16", but then you knew that already.
Good luck!
Steve
