Tachometer trouble

I'm having basically the same problem as in this thread.

Since I've had the car (about 2 months and loving it) the tach has just gone to about 4K and stayed there whenever the car was on. Today I decided to try to figure out what was wrong with the tach and took it apart. I found that the wiring had been fooled with because there was 2 white wires from the little harness that were just looped back on eachother (they had been cut before) and then on the yellow wire someone soldered on some sort of variable resistor or limiter(it had a little dial and when it is turned, the tach goes higher or lower).

All that to say - I'm not that interested in keeping the origional tach, so what tach could I get to replace it (autometer?)? Any experiences? Any links to the gauges you bought or prefer? Am I going to have a hard time wiring it correctly?

Thanks for the input.

Matt