Reply to "want to make my own flasher circuit to replace 154C"

@Mallard4468 posted:

In that diagram, am I correct to assume that the purpose of the resistors next to each LED is to limit the current to the voltage they require?  If so, can the circuit power incandescent bulbs if those resistors are removed?

Good guess, but the short answer is not really.

In this circuit, the resistors form a voltage divider between the power source + and - that allows the 555 output to toggle between high and low voltage states, without directly shorting it to either source pole.  The LM555 can not directly drive a source that draws more than 200mA, like most incandescent bulbs.  The 555's output is intended to trigger solid state device inputs (diodes or transistors) or possibly a small relay coil.