289 Emissions Heads

I know this is a simple issue with an easy fix, it so happens it's the smallest things that create the biggest problems for me.

I'm working on a 66' California 289 that I just put back into a 67' Mustang. The owners of the car I'm working on has a pair of headmen headers that they would like to use, however because of the air injection, the capped ferrule nuts stick out and hit the flange of headers, which are not designed to be used on those heads. My question is, has anyone come out with a plug for these heads, or is there any other course of plugging the heads other than a bolt, and then grinding down the header flange (which really isn't an option). ?