swaybar sizing
no clue as to the part number, nor does it really matter.
when I was first educated about the different swaybars on the SHO (see many postings as well as SHOtimes post on this), I thought that perhaps I needed some special tool to measure the diameter.
The simplest and most idiot-proof way is to use your open-end wrenches of diameter 21-26mm and see which one gives the snug fit. also helpful is that 15/16ths is 24mm, and 7/8ths is 22mm, in case you have only std wrenches. A good set-up for a daily driver is the time-honored 24mm front/26mm rear swaybar pairs. Your 93 probably does not have these, but you can get a set from any Gen 1 (89-91) SHO. A little paint and they are good as new. With the 24/26 setup, you get a nice solid ride with comfortable understeer.
suspension jobs done well often are, to quote many a mechanic, either "all or nothing jobs". A good start is to replace not only the swaybars, but upgrade to TPR bushings all around and replace the front/rear end-links also. This is money well spent, and within reach of most do-it-yourself-ers.
the 94/95 spindles are nice. If you have the front set, you can do the 96 brake upgrade for limited funds (just need the brackets, pads & rotor off of a 96 SHO or new from auto parts store). This was one of my first home-mechanic upgrades on the SHO and is one of the best "bang for the buck" you can do.
JD
89 GL/SC (retired)
95 ATX
95 MTX