What does Bosch spark plug R3 Part number4418 cross to for an NGK spark plug?

yes

Use a timing light & see if it flashes. Current through the wire is what flashes the light. Hold the boot with something insulated with terminal near the plug & will jump across the gap while...

If you know that there is spark at the distributor cap then I would think it would be bad spark plug leads.

To answer this question it would be helpful to have more information for example if your vehicle is older with high miles a worn out distributer can cause this problem

Faulty coil, or coil pack (depending on the vehicle). If your vehicle is quite old it might have a mechanical distributor (looks like a miniature milking machine with plug wires coming out of the...