Here is what I use, inexpensive. Only one lead wrapped around the coil/plug wire about 2-3 wraps, programmed for 4 pulses. Has internal battery. The lead is long enough to mount inside, a lot of inexpensive battery tachs have short leads, not long enough to mount it inside the A. There is a backlit version available. Updates every 1/2 second or so.
https://www.amazon.com/Trail-Tech-74...s%2C225&sr=8-1