Thank you, will have a look at them.ICC has gateways that can be configured for Modbus to Modbus conversion and can remap 4X registers to 3X registers.
For Modbus RTU, I recommend our Mirius gateway
http://www.iccdesigns.com/protocol-gateways/66-mirius.html
For Modbus/TCP, I recommend our ETH-1000 gateway
http://www.iccdesigns.com/millennium-series/10-eth-1000.html