Best way to start building a 460/503?

[AmericanPie]

Newbie Here!
I was referred to this site last week by some local Cobra guys, and first of all I must say. . .you guys ROCK! (I just had to say that.)
I've been bitten by the Cobra bug and am starting to plan the buildup of a 460, possibly to a 503. From the info I've gathered about the factory crate motors there are some things I don't like (they all have 2-bolt mains, for example) so I'm wondering what is the best foundation for a really special Ford big-block.
Should I use the factory siamesed-bore block (#M-6010-A460) or one with full water jackets? Or rather than building the motor piece-by-piece, would it be far more cost-effective to purchase a crate motor (521?) and discard the parts I don't want?
And how about heads. . .are the factory ones (#M-6049-C460) the heads of choice or are there better ones available in the aftermarket? Should I buy bare heads and use aftermarket hardware?
Please be patient with me; I've had plenty of experience building big and small-block Chevies but know very little about Fords. I'm beginning to remedy that situation with your help. Thanks!

Larry