Try....
www.fordracing.com
Go to performance parts once you're in there.
Other than that, I don't know any off the top of my head.
There's some Winston Cup blocks on there....of course they're capable of handling 850hp +....but you have to pay for them.....probably around $1500-$3000 depending on what combo you want....aluminum or cast iron....dry or wet sump....9.200" deck height or 9.500"....Windsor main bore or Cleveland...etc...
So you're planning on having all this done by spring?