The rx3 is leaf spring, the rx7 sa and fb are a 4 link and coil springs. The rx3 71-75 had long third member 24 spline, 76-78 short third member 24 spline. Sa's 79-80 had short third member 24 spline(will fit rx3 housing all years but will need 76-78 drive shaft), fb's 81-83 same as sa's, fb's 84-85 short third member 26 spline. hope that helps and or answers your question.
1982 rx626 20bt, a/t, a/c - project in progress
1979 Great Little Car 12a bp , Twin 45 DCOE., gslse susp. - driver
1973 rx3 6.5bt spp - next in line project Dr. Jekyll
1973 rx3 26b pp - third in line project Mr. Hyde