73 Regal 455s, are they all the same?

[sharkmonkey]

What's the deal with 455 Regals from 1973?
Are they all the same? What's the specs?

I know this Regal has a 455 with a "U" code.
Did they all have posi? What's the rear-end gear?
My brother bought this and I might be getting it from him after we redo the body and paint.
Thanks,
MARK

Here's the link:
http://www.atzauto.com/buick

[sharkmonkey]

Okay then...
How about putting headers on these. Is it as difficult as the G-Body Regals?
MARK