So, if you did that i assume that you found out all the programming for the lines and exts after the 400e&m are messed up.
Its not like Norstar where there are hard ports. The Legend bases ports on what is in the system.
If i had a system with 2 408 cards (4 lines 8 exts) my first ext would be in the first port of the first slot (ext 221) with 229 being the first ext in the 2nd slot. ALSO, line 1 would be in the first slot and line 5 would be the first line of the 2nd slot.
NOW, if i put a 800 card in the first slot that changes all programming. Now the first slot of the system is a line port. So ext 221 gets moved to the first port of the 2nd card. And, line 1 is in the first port of the first slot, but instead of line 5 being the first line in the 2nd slot, its now line 9.
since you are putting a 400 card (4 lines) in place of a T1 card (24 lines) All line programming after that will be royally goofed up.