The guy I bought my Swinger from has a restored Notchback. He took a original battery, drained the acid, cut out the bottom (I think), and put a John Deere Lawn and Garden battery inside.
Yep with the battery hold down will hold the case in place. The bottom would be the place to cut it open.
The restoration battery case seems to be a little bigger than the normal modern day battery.
It should cover a battery just need to figure out the terminals.