Custom recipes/conversions per world

I wanted to make a machine that would turn a certain item into another randomly per world, except I can't figure out how to.

example:
I have 6 items, item 1, item 2, item 3... etc
possible conversions:

item 1 <> item 4
item 3 <> item 2
item 6 <> item 5

the recipes would make should they can be converted back and forth (item 1 to item 4 and item 4 back to item 1) and they wouldn't have overlap issues (item 1 to item 3 & 4, or item 1 to item 1). These conversions would be completely random per world (world 1 could have item 1 to item 5, but world 2 could have item 1 to item 3)
Any suggestions on how I could do this would be great!