Making my own ipv6-ipv4 router?

[Obi-Lan]

I got one static IPv4 address and one /64 IPv6 subnet from my ISP. They apparently use radv and my boxes are getting their IPv6 addresses quite nicely. ISP even offers DNS servers with IPv6 addresses to use. Now my biggest problem is that not everyone has AAAA records or IPv6 addresses so I need IPv4 gateway of some sort. I know about sixxs.net having IPv4 gateway and it works when you type google.com.sixxs.org (but gmail isnt) but that sort of solution isn't nice to use.

So I wondered if I could use router, give it one IPv4 address and one IPv6 and put the rest of network behind it. But since I have about 18 billion public ip addresses I don't want to use any kind of NAT solutions. Can I do some IPv6 routing stuff with /64 prefix? I read some pages telling about /48 subnets and dividing it to /64bit network would be the way defined in standards. And I was wondering does linux realize, if host has only A record, when to use IPv4 and when IPv6?