TMG Multiple External IPS

Hi all.

I have already read resources so just need to confirm something

We have router connected to internet with multiple static IP address.
The inside of this router is connected to out TMG box as and internal address 192.168.1.4
We  Migrated our ISA 2006 to TMG by exporting and importing config
we repclaited network cards and statically assigned smae ip addresses ( in this case 192.168.1.4 for router address)

But now we can no longer access a website that exists on a client site in which they had already added rules to their firewall for our static address range

Would this be a configuration on the TMG box. ( Someone stated you would add these addresses to the NIC for ARP
Would i have clear the ARP table of my router, so the IP address is registered with the new MAC address.

So effectively how do i get my requests from TMG server to present on the internet as one of the static IP addresses - the router nor the Router nor the NIC IP has changed, just TMG