[TempoMat]

Well I managed to do it.
It was in the end easier than I thought, due to the fact that only numeric string were hashed.
The solution was:

For i=11000000 to 99999999
    res=SHA1(i)
    for j=1 to lenHashTable
        if res=HashTable(j)
           Write2File (i=HashTable(i)
        end if
    next j
    Append2HashedFile (res)
next i

It took approximately 2:30 hours to finish on an old Core i3 330M Laptop.
Every 500000 SHA1 hashes generated was saved to a file was which had a size of approx. 27,34 MB.

PS:
The start value was chosen to be 11000000 because the range from 10000000 to 10999999
was used in the testing of the program which yielded no collision with the hardcoded hashes.