I JUST finished installing a sunbird tach myself. The resistance needed to properly calibrate the tach is around
200,000 ohms, or 200kohms. A variable resistance trimmer aka potentiometer is needed to fine tune this resistance so that your tachometer reads exactly
as it should.
1 meg ohm is equal to 1,000,000 ohms. So, a 1 meg trimmer can be adjusted from 0 to 1million ohms. Basically, you need any trimmer that exceeds 200k.
For my tach, I ordered this trimmer assortment off of ebay
. Both the 1meg and 500k timmers in this assortment will fit your needs. I opted to use the 500k as it gave me a greater degree of adjustment to fine tune my tach readout. Each trimmer has 25 turns between full resistance and zero resistance, the closer the resistance is to what you need, the greater degree of adjustment you'll get for each turn of the screw on the trimmer.
'87 GT 3.4 pushrod daily driver
'88 GT 3.4 DOHC swap in progress