As you can see from the picture (I hope), I attached a 1/4 inch aluminum plate measuring 10" x 4" . I super glued it to the bulk head with permabond glue (had some around from head gasket job), then drilled for and mounted 1/4 inch pop rivets along the perimeter making sure not to interfere with motor or chains. I then drilled holes in the bulk head where original mount screws were located, big enough to accommodate the bolt heads which replaced the original screws (approx 5/8"). The motor/drive can be replaced by removing their mount bolts. The plate is a permanent fixture.
I appreciate all the ideas passed along in this thread. They served as inspiration to complete this job. Thanks!