They bolt up but the square ports don't match the new heads.  You need to do a bit of grinding to come close to matching the "D" ports on these engines.  You will not have 100% match but you can get close.

I used a Dremel and a carbide bit to open them up.  Final cleanup and shaping was done by a rounded file.  It's wasn't as hard as expected.  The little Dremel turned 30K RPM and rapidly cut away the cast iron. 

The end ports on each manifold go quickly.  The center ports take a lot of time because the cast iron area that needs to be removed is about 3x as thick as the end ports.