We are using 8 rack mounted MT2834BRs on one end and MT2834BAs on the other end, What configurations/settings are needed to make these modems work on 4 wire leased lines (instead of 2 wire)?

The MT2834BA and MT2834BR modems do not support 4-wire lease line operation, they support 2-wire lease lines only. We recommend the MT2834BLR and MT2834BL for this application because they support 2 or 4 wire lease lines.