Spark plug thread inserts

[MPHRACING@aol.com]

I am in the process of repairing a set of cast iron Ford heads that the spark 
plug threads are stripped.  The original thread is a tapered seat 14 M.M. 
thread.  I can get thread inserts from Time Fasteners to repair the thread to 
stock, but that requires the head be tapped out to 18 M.M.  Would I be better 
off 
just to tap the head for 18 M.M. and use an 18 M.M. gasket type plug.  The 
engine will be using an 871 blower.  

MPH Dave