Hi Forrhouse
Just seen your post so, sorry about the delay in replying.
SSL generally used Brandrex twin screen cable in their consoles which was 7/0.2 (7 strands of 0.2sq mm). This is the black balanced cable which later became OFC (Oxygen Free Copper). This was used for all their patchbays and signal wiring including patchbays and 104 way MRAC connectors.
As you probably know, SSL used 96 way ITT DL connectors for their installation connections. If your two 651 centre section MRAC connections have been cut, I would suggest using 96 way DL's or perhaps some 56 way Edac connectors instead of a larger 156 way DL which is very expensive and rarely used apart from industrial purposes these days.
A 96 way DL would almost house all the wiring on a 104 way MRAC and 2 x 56 way Edacs would certainly be able to fit 2 x 16 balanced circuits from the 651 quite easily.
Hope this helps from Jim Lassen (wiring moderator on this forum).