I know I mentioned my preference for new items before, which is why I have
"new" MSD injectors all around.  To fit in the stock primaries, I had to
make a bushing to fill in the difference between the holes in the center
housing, and the smaller-than-stock MSD injectors.  The top fuel feed of the
MSD is actually larger than the stock injectors, so I had to bore out one of
the fuel rails for the primaries.

For the secondaries, I bored holes in Mazdatrix intake, using the existing
casting pads.  I used a fuel rail from TWM for the feed.  So far, I'm really happy with the way this turned out, and I'll never go
back to old stock injectors.  I'm sure almost any injector can be used with
the proper fabrication, and those mustang injector deals sound great.  I
already had the MSD's, so that's what I used.  Cheers,
Rusty (not safe to drive cattle trucks through the tunnel in Mobile, AL)