I chose the ford for the available ratios. I think the 94+ 7" mazda rear would have been adequate otherwise. 3.636:1 ratio is not available in the U.S. Readily available in Austrailia. Forget anything numerically lower.

 I bought the 1996 ford thunderbird complete rear subframe for $100 including the driveshaft.

Broached miata hubs are required to fit ford outer cv spline. Requires specially made expensive broach for the 28 spline cv's. Mark Williams machined my hubs for around $130 shipped.

 Mark Williams will make 300m axles for around $550 a pair. Moser made my axles for $160 each(not 300m).

Shorten and balance driveshaft. I pay around $100 including balance locally(Big Moe's in Lithia Springs). 

Custom mounts. Fronts are .250 plate. Rear is a combination of .125x1" strip, 2x2 .125 angle, 1" round DOM tubing, and .250" mounting plate. OEM ford bushings and rear mount are used.

Outer cv spacers are needed on the ford cv's to fit the miata wheel bearings and dust seal. Mine are .240"thick, 1.20"I.D., 2.00"O.D. cut from 1/4" steel plate on a lathe.

91-95 ford taurus outer cv boots should be used for shock clearance. The lower shock pocket should be moved inboard on the control arms as well.