The Chrysler tach drive will get you pretty close to that. Whether it shows as a flat line or a slight rise intiming will depend on two things. One, adjustment of the secondary spring perch. The other, speed of the ECU's electronics and other factors that may slow the firing time. That SB unit that I showed the plot for was tested on a SUN 404 with an amplifier box. That box is pretty slow. Still flatlined.
