The 93 did have provisions for a tach from the factory. You didn't say if you reused the Dodge harness or the chevy. But it doesn't matter.
Most aftermarket tachs are looking for a 9 to 12 volts square wave signal. Square wave means on and off. There are a couple of ways you can do it. The alt pickup is one. You know about the AutoMeter 288 tach. Many 1st gen drivers use it.
The next way would be to glue a couple of magnets to the balencer and use a magnetic pickup. Any good electrical supply house can get you one. MFG a bracket to mount it to the engine. The 93 crank sensor is mounted at the 11:00 position on the engine. There are two standoff type studs there for that reason.
If you reused the Dodge harness in the chevy. The tach harness is located by the steering column on the left side. It is a small flat black 4 wire plug.
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93 W350 w/duals, fuel pin turned, 6X.018" injectors, 4" exhaust, 3" air intake horn, Super HX40/16, auto, 3:07's axles, 2" skyjacker lift, B&W flatbed