I use a cheap SunPro 2 1/8" dia tach on the column. No matter what tach u use, make sure the gnd wire is attached first. My 221cu motor runs abt 2000rpm at 40 mph with stock 4:11 rear.
t-moss1, I agree with 4dFord. If you desire a vintage tach snag one off of eBay and let Williamsons do their magic. They've done 2 for me and I'm well pleased. A 5 year guarantee to boot! If you want the particulars of which tachs to consider let me know. http://www.williamsons.com/Dennis/Arkansas