[Bad News]

All the spread port intake will interchange, 18 14 11 etc. The intake manifold faces are all the same angles, the degrees are referring to the valve angle from deck surface.

 

[Bad News]

When I worked there ONLY the 18* intake would work with the 18* heads. ONLY 14* and 11* heads shared an intake. 18* head castings were there own and 14* and 11* heads shared the same casting.

OLD 18 degree castings (1990's) were not spread port like the heads available now.

CURRENT 18 14 11 12 share the same spread port configuration. An 18 degree spread port Dart manifold bolted to my 22538816 OLDS 14 degree heads.
Some are square port some are oval port. Intake manifold face angle will be the same.
A profiler spread port manifold will bolt to 18,14, 12, 11.