My car is a 400 with 1970 #11 heads and runs pretty good. Thinking of an upgrade to better heads. You do know you have to drill and tap threads for headers? #11 heads don't have the outer bolt holes drilled on the exhaust. Definitley go 400 build I had less than $1200 in my build. That was having crank turned,freeze outplugs,cam bearings installed. It didn't need bored so just a good hone job. Heads were bought from the machine shop for $225