I'm sure there's an easier way, but let me analyse the problem first. You can have 6 chars (incl. no spaces), 7 chars (incl. no spaces) 7 chars (incl. 1 space) 0r 8 chars (incl. 1 space). OK now here's the multi-stage approach.
You can use the function 'LEN' to determine the length of each, then you can sort of this result to isolate all the 6s and 8s into separate lists. Leave the 8's alone but split the 6's into 2*3 char fields and insert a blank field then merge the three into one. Now for the 7's.
Split into 7 individual columns and sort on column 4. All the top ones will have a space in column 7 - these are already ok - remerge the fields. All the rest need you to insert a blank single char field and remerge.
NB to create a single char blank, use " ".
Haven't tried this but it should work. Good luck.