Block Display / Item Display Summon Entity Help

Making a display case and thought I'd use the Block Display or Item Display as armor stands not working as I expected. 

My questions are:

1. How do I check for item or block? If item in inventory slot 1 is item, do item display and if item in inventory slot 1 is block do block display.
2. How do I set the NBT tag of the block_display or item_display to what is in inventory slot 1?