When you use Autolite's heat range reference chart, the 103 shows up as the replacement for the TR6 and BR7EF plugs. Under Autolite the heat range is D14. It is slightly colder then the TR6.
BR7EF reference,
http://www.autolitecatalog.com/Compe...=br7ef&em=True
TR6 reference,
http://www.autolitecatalog.com/Compe...pn=tr6&em=True
As you can see, the 103 is the coldest plug in that heat range.
