For general peace of mind:
* Check each fuse in the fusebox - they should be sitting in place nice and tightly with no corrosion. These fuses are cheap and commonly malformed - obviously the metal end caps, not the plastic body of the fuse, should be the parts that make contact with the fuse holders.
* Check that silly earth rose thingy armoore mentioned, near the battery on the 'strut brace' firewall
Specific to the rev counter problem:
* Check the plugs and wires connecting to the ignition coil. Some of these plugs are badly made and don't grip on securely. If in doubt about any plug in your 33, cut it off and replace it.
Specific to the speedo problem:
* Do not remove the sensor from the gearbox except as a last resort - I'm told it's fragile, plus it's unlikely to be the problem (possible though, of course)
* Check the cable from the gearbox sensor - it's grey, I think, and it passes through the first firewall (check for damage here) then plugs into the wiring loom at a black 3-pin plug between the brake booster and the ventilation unit. Undo this plug and check for corrosion.
Specific to the 'maine lights' not working:
* If you mean headlights, do they work on high beam? If so, tap the two big relays mounted to the body of the car on a separate block near the fusebox, tucked away almost under the windscreen. One's for the wipers, one's for high/low beam on the headlights.
* If you mean instrument lights, check the fuses in the fusebox. Fuses don't need to be blown, they may just not be making contact.
I recommend that a multimeter, pliers, a crimp tool and crimp-on terminals, and some form of electrical spray (e.g. CRC, WD40) are all things that 33 owners need.