At point "A" is where the large rear foot of the Miata seat runner,runs into the arch of the floor pan, limiting reward placement. This foot/tunnel contact also causes the door side seat back pivot to hit the trim molding. So this foot will be trimmed/removed to let me move the seats ~1" towards vehicle center for door clearance.

because of foot, pivot is tight on door trim

There is about an inch of clearance on the seatbelt
mount. So removing the foot will let me move the seat
to center and clear the door properly.

With this position test fitting, you can see the Miata seat original front mount points are extremely close to fitting the original Spitfire floor holes. The little washers on the carpet, under the legs, are the original Spitfire washers still stuck down in the carpet. The slide adjust handle is nearer the center console.

       With the fronts almost directly on top the original Spitfire mount holes, even the rears are pretty close.  You can just see the washer on the carpet, through the rear left Miata seat mount bracket hole. This left foot contacting the tunnel (dimension 'A') is also the problem I need to deal with to move the seat inboard one inch to clear the door side pivot completely.