In addition to the RJ11s, the GXW4248 has two 50-pin female Amphenol connectors.
If you’re lucky, the 66 blocks have Amphenol 50 pin connectors. Just get a couple of pre-made 25-pair cables to connect them. If you’re not so lucky, buy cables with 50-pin male on one end and the other end bare. Punch the bare ends down to the connectors.