Question

find two numbers that has as estimated sum of 6, 000 using the digits 1 2 3 4 5 6 7 and 8

Answer 1

Try pairing numbers to make a sum of 9, after taking out, say 1 and 4 for the first digits.
leaves 2,3,5,6,7,8,
so pair 2,7, 3,6, 5,8 for the other digits.
making
1235 and 4768
sum is 6003.

Try other combinations to see if it is possible to get closer.