Ten years, I would try a fresh set of coils. NH or G ? I drain my carb & tank sediment/feeder monthly during driving season. This new corn gas is hard on parts, I also add some non-ethanol Trufuel on every fill up.
In years past I had some starting issues but those went away after installing an Optima in my T.
You can never have to many "nice TIGHT clean grounds", check those cables and what is helpfull is an addition ground wire off the starter "if you have one" to the frame, dirt and oil add resistance to the circuit. Good luck and let know how you make out with your 23.