194944

We found out that 6 could only be placed in the bottom row because it was the largest number and it couldn't be the difference between any other numbers.
Our 5th and 6th attempts were the only ones that were effectively successful.
Numbers that we found couldn't go together were 2 and 4 because there is a difference of 2 and there was only one 2 on top of that 3 & 6 because the difference is 3 and again there is only one of each number.
We found 2 solutions:

1
4 3
6 2 5

and

3
1 4
5 6 2