MG Car Repair: 1978 1500 EGR, british car club, thread size

Question
Howard - I inherited my father's 1978 1500 Midget several yrs ago.  Last year
just before putting it up for the season, when I started the car I heard a pop
and then the exhaust got much louder.  
I have found the issue to be that someone before me removed the EGR and
had the hole on the manifold where the EGR threads into stuffed up with
something that finally blew out.  How do I plug this hole?  I don't have the
EGR and the threading is super-fine and I can't find suitable plug.  I think
taking the manifold off to tap a new thread there could be a huge problem -
any ideas?

Answer
Ted, I don't have anything that tells me what thread size that is but I do think that you could measure it roughly and go to a bolt company and purchase a few short bolts and possibly find what size it is.
If that fails you should contact your closest British car club and if they have a web site ask to put in an ad for that fitting. I doubt you will find that fitting in any of the MG parts companies.
Or just take the manifold off and rethread it to a size available. Taking an intake manifold off is not a big job.
Howard