will 1967 #670 heads fit on a 1976 pontiac 400  

Yes, but compression ratio will jump from 7.6:1 to about 10.5:1, so your octane requirements will go up as well. However, if fed adequate octane fuel, the hp and torque will increase greatly as well. Some people have luck using 93-94 octane fuel and octane booster, but often even retarding the timing won't stop pinging and internal engine damage, so be careful. Try reading the tech articles on Rock and Roll Engineering's site, there is a great article about octane requirements and compression ratio there.
http://www.pontiacpower.com/index.html
A lot of people don't like his opinions but they make good mechanical sense and you won't go to wrong following his advice.  

Hi thanks for the info the air port is not far also some race teams close  

By all means, if you can afford the octane, have at it!