i also have a 1973 non smog 400 bb that i beleive came out of a firebird. it has the x6 heads on it but im not sure if those are the good heads or not. it is a complete motor from carb to oil pan, im asking $400 or best for it, i really need to get rid of it.
Jessie

 

How much NOS would that mtor handle? Beeeeech.

 

im sure as much as you can give it

 

6X heads are on `77-`79 400's and some 350's