I'd add:
1) Make certain all the bits are cleaned and properly lubricated. A-1 problem with dizzys is improper lubrication and build-up of grime under the breaker plate where you normally don't look.
2) Unless you rally and jump the 'ol girl, the rear axle rarely goes to full droop except when you jack it up to change tires. A small "wow" in the pipe will allow it to go under w/o interference.
3) & 4) Yup, OK. Might as well optimise the valvetrain while you are there. Money spent on the intake/exhaust ports is well spent here to take full advantage of the more effective exhaust pipe.
I'm not convinced that a rear sway bar is a good idea on a solid rear axle car but that is a matter of opinion. Generally, heavier rear springs will provide the same effect without providing oversteer at the limit that a rear bar tends to induce.
Another area to cheaply assist performance is to reduce parasitic losses. ensuring that the drive-train is up to snuff and well lubricated will help there. Use of synthetic oils has proven to be effective (but conventional wisdom says not to use them in the O/D tranny... I'm still a little skeptical but...). Replacement of the engine driven fan with an electric one, altering pulley size to under-drive the water pump and alternator. Alternator instead of generator, etc...

Mike!