Let's get one thing straight:

You can bolt up a pair of late exhaust man9ifolds that have the AIR passage in them, to an early head OR a late head with the AIR ports in the head plugged, and it'll be all right. For example, my '86 318 had the AIR ports and exhaust manifolds with the AIR passage in them.

Some day I plan to run headers so I plugged the AIR ports in the late model heads. What about the exhaust manifolds? The AIR passage in the exhaust manifold is completely separate from the exhaust gas passages. So I can run them for the time being on the heads with the plugged AIR holes WITHOUT any leaks out the exhaust manifold. That's with the hole on the end of the manifold there the AIR pump should be hooked up, open.

Too many scare stories out there.

R.