The answer to your question is ........ "depends."
I built competition Toggle Link rifles for over 16 years. My council to my customers was always the same. the biggest bang for your buck is/was a good, quality action job. Uberti rifles were/are notorious for heavy springs. Heavy to the point they cause accelerated wear in the moving parts. Not to mention, those same springs made the rifle "unfun." Judicious rubbin "n" buffin, and tuning the springs down to more reasonable levels made those rifles very user friendly indeed.
The Japanese made copy of the '73 isn't much different. Judicious internal rubbin "n" buffin and tuning the springs to an effective but user friendly level is your best bet. I'm not impressed with all the "junk" included in the Japanese firing pin extension. Switching out to the extension made by Pioneer can't hurt. That one change may also not make a noticeable improvement.
Now the hard question. At what level of CAS do you want to compete?? The Super Short Stroke kit makes a measurable difference in the speed at which the rifle can be run. If the primary use of the rifle is CAS, in all honesty, the SS kit makes it more fun (once you learn to run it). Pioneer's kit is a quality product. It does however take careful instillation and adjustment. Done right it's a treat.
You may well find you can run your rifle righteously fast "as is." Going faster WILL get expensive.
Coffinmaker