It's always nice to give good news, so here goes:
As long as you get a tach from a Camry with the same engine, it's a simple plug-n-play. The tach wire is already in your harness, it's simply not connected to anything now. If you can find a tach guage cluster from another gen2 Camry, just swap it in. I can't even imagine how anyone drives without one (but then again I've never owned an auto trans)...
If you can't source one at a wrecker, try eBay...these things are plentiful, and usually pretty cheap. Good luck!
--Tim
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1990 5spd V6 Camry (Still kicking at 393,000km) 1991 Celica GTS -- Pappa needs a 3SGTE...and AWD for all this friggin' snow
Honda my A$$, you just can't kill a Yota...