There are several harmonic orders in which dangerous vibration will occur at different RPM levels. Operating an engine rapidly through the RPM range is almost safe even wih no damper at all (blower pulley only) since the exposure is literally 10ths of a second for each.
However: if your orders are very close to your stall speed or trap speed: problem.
The number of orders that will occur (both above and below your RPM range) varies with the engine design (V or in line), number of cylinders, overall crank length, size and number of main and rod bearings, stroke, number of main bearings (not all the same value contribution).
Things that raise the RPM of each harmonic order:
Short crank (V4 obviously best, L8 worst)
Big rod and main journals
Short stroke
5 mains for V8, 7 for L6

Sample calculations for my book project (Chevy 235" stovebolt L6) with 3.9375" stroke, 2.3125" rods, 4 x 2.73" (average) mains, a relatively weak and flexible crank, has a crank frequency of 216 Hz (cycles per second), giving significant harmonic orders at:
9th order occurs at 1,440 RPM (even higher orders are below idle speed)
6th @ 2,160 (weak, but avoid it anyway)
3rd @ 4,320 (very strong and dangerous)
2-1/2 @ 5,184 (strong, but above typical use)
2nd @ 6,480 (never reached)

Never gear the car to sustain these engine speeds! Avoid them, or pass through them.