Correct understanding of NAT translation through Cisco 2821

Here’s my scenario:
WAN switch(150.121.10.50)

Current router config –
Cisco 2821 outside GE0/0 = 150.121.10.51 – connects to WAN switch
Cisco 2821 inside GE0/1 = 201.50.10.10 – connects to inside LAN switch which firewall connects to.

Firewall outside interface = 201.50.10.11

What I would like to do is remove the firewall(which is handling the dynamic NATing now – all inside systems are translated to 201.50.10.11) and simply have a few systems with internal IP address connect to the switch and which connects to the inside interface of the router. However, I would like to keep intact the same translation of all internal IP address to the one 201.50.10.11 address.

Can this be accomplished and how?

Thanks,