Bill, this will be my last post regarding your 455 as you aren't listening anyhow.
6X-4 heads, which were low compression 350 heads, are good on a 400. 6X-8 heads, which were low compression 400 heads, are good on a 455.
Buy what you want but don't complain about performance or tuning issues, or how you've been "ripped off", if you don't do your homework and decide on what you are building before you start shopping.
Yah. Bill is right on with his research and Yellowbird is mistaken. He asked all the right questions when buying the heads. He bought my 6X-4's. They were the original heads on my 79 TA WS6 4 speed car. For a reference, look at the last head listed on this chart. http://www.pontiacstreetperformance.com/psp/heads.html
