I think your proposed rule is maybe more restrictive than you want, because it restricts this redirection to connections that originate on 192.168.0.54. Perhaps a better choice would be
#iptables -t nat -A PREROUTING -p tcp -d 192.168.0.54 --dport 80 -j DNAT --to-destination 192.168.0.64
Depending on the other rules in your firewall configuration, you will probably need the following
#iptables -A FORWARD -i eth1 -s 192.168.0.64 --sport 80 -j ACCEPT
#iptables -A FORWARD -m state -p tcp --state ESTABLISHED -j ACCEPT
The first of these additional rules allows the first reply packet from your web server back through the firewall, and the second rule takes care of any further communication on that connection. If your firewall machine is itself
In addition, if your intention is to re-route external HTTP requests to an internal server, you will need some sort of DNAT rule to masquerade the private network address (192.168.0.x) that will appear as the source in any reply packets.