Good advice above & I'm repeating some of that here.
1. Turn signals - there are TWO flashers, one for turn signals & one for "4-way emergency flashers". If the emergency flashers work, then you've determined the bulbs are all good already. If the dash turn signal lights come on, then it's most likely the flasher itself (swap with good emergency flasher to test) or the turn signal switch in the column (check with electric meter vs. the wiring diagram at one of the two plugs at the bottom of the steering column...the smaller one I think).
2. Gas gauge - could be sender inside gas tank, gauge itself, the dash cluster circuit board or the wiring going between the sender & the dash cluster. Usually, the first step (with dash installed) is to ground the wire at the sender with the key on & the gauge should go all the way full...but you have the dash out already. You could check continuity from the sender to the wire at the dash (green?). REMEMBER the dash only takes 5 volts (voltage limiter in dash), so don't use a 12 volt source. I'm not sure how to check the gauge with the dash out? If it's bad, the dash would have to come out a 2nd time. ANYONE KNOW HOW?
3. Blower Motor - just run 12 volts + ground to it & see if it turns on. If yes, then it's the switch or possibly wiring that's the problem. Blower motors commonly burn out.
4. Wipers - have their own wiring harness (top plug on bulkhead disconnect) with 4 wires (at least on 3spd wipers). Check vs. wiring diagram & run 12 volts to appropriate wire(s) from under the hood to see if it moves. Also check the ground which should be a little metal strap on one of the wiper motor bolts which grounds to the body. If that all checks out, then it's most likely the wiper switch OR a connection at the bulkhead disconnect.
Everyone, please feel free to jump in & correct me or add more info.
Hope This Helps
One more thing, it's not all that common of a problem, but you could check the 8-prong(?) plug behind the driver's kick panel which has wires for the back half of the car (turn signals, emergency flashers, gas gauge, etc.) which you could check for corrosion or bad connections.