I had a set of those on my 1964 Plymouth Savoy with a 440 dropped in it. I can tell you that the hood gets a little on the hot side above the manifolds.
Also, I'm going to have to measure the engine in my 1964 and compare it to my 1968 because I was told the by a well know magazine writer that if I put the later cross member under my Plymouth the engine wold mount higher and further forward. That's opposite of what you guys are saying.
I have an old Hot Rod Magazine Spotlite book on the Max wedge cars. The cover photo includes a 426 stage three with the square tube manifolds that I personally have never seen on a production engine.