So nobody else does what I just did, let it be known that the MSD injector connectors will not fit on the Mazda 550cc injectors without major modifications.  There is two main problems with this connector.  First, the pins are centered in the connector, which isn't the case on the injector (but they can be bent).  Second, the connector is squarish and the 550cc injector is oval.  That's like putting a round peg in a square hole.  There are a couple of other minor problems, but these are the biggies.

Note that they do fit the 460cc injectors with very slight modification to the injector or connector.

But the price is right!

Mark S.