I have to agree Nash, IF, you fins a 421, or a 428 for a resonable price, snatch it up! They are great motors with the best of both worlds so to speak.
I had a 421 in my 68 bird and it was by far the fastest car I've had to date. I never lost in that car, and all my buddies from High School still love to talk about the old days in the bird, and how they could never catch it... best smoke shows... you name it. Man I wish I still had it...
They make aftermarket 428 & 455 emblems to fit the stock pin hols of the 400 hood etc. Personally, I like having the 400 emblems with the 455 lurking under the hood, and for the most part, no one knows the difference if they don't start checking the numbers. Even my Performer intake has all the Edelbrock marking ground off, and it's painted to look stock. I love the modifications, but like it to appear stock...
Anyway, like I said, if given the opportunity, jump on it if it's a resonable deal.