Okay- here is my $.02. What I was told by several people as I was building my car is also what makes sense to me:

The upper and lower links are locating arms, not traction bars.

The popular setup I have seen is:
Add a tri-link to the top of the axle. This is an added traction bar, there is no question it is legal.
Replace the bushings on the stock upper locating arms with soft foam. This effectively renders them non-functional, and it is clearly legal.
Replace the bushings in the lower arms with spherical bearings. I personally think the interpretation of the old GCR wording "any bushing material" meaning spherical bearings was legal was crap. Now the wording has been changed in the GCR and it is officially legal now without argument. The Mazdamotorsports part listing for the bearings is below.

Nowhere do I see allowances to replace ther locating arms or the ends. Just my opinion.......but it seems to be the common interpretation of the folks I race with.

0000-04-7422 C BRG KIT,LOW TRAIL. ARM 1 ALL RX-7 1979-85 $263.40

Kit includes four (4) spherical bearings to replace stock rubber bushings in lower trailing links. Requires pressing rubber bushings out of stock links. Uses stock bolts. Legal for SCCA 'IT' classes. Recommended to use with old, soft, upper bushings to prevent binding. Kit also available via special order that includes modified lower trailing links, fitted with sperical bearings (0000-04-7423).