Sorry Mattias, I don't know about the Mytek.
From what I remember, we bought just the card kit from SSL and I put them in boxes. Think we had 2 of them at Whitfield Street.
All three studios were wired up for S29 standard, even in the Neve rooms, this meant any tape machine could go to any studio, especially the 3348's.
If you just want transport control from the SSL without computer mix control, then no, you don't need anything special.
If you want Tallys from the 3348 switch lights, then you will need to implement the level shifting ciruitry