How to wire Lionel 154 Crossing signals to Lionel 153 IR

Jerry, connect one of the gate terminals to a transformer ground or to the ACC GND terminal of the 153.  Connect the other gate terminal to the NO (normally open) terminal of the 153.

A IR will not operate a postwar 154. It will light both lamps at the same time if wired together, but will not alternately flash the lights. A modern 154 with the flashing circuity built into the base will work.

What Chuck said.  If you have the PW 154, it will have 3-terminals.  I believe Danr is referring to the "modern" 154 which has 2-terminals and can be directly connected to your 153IR per Lionel instructions:

You need to add a flasher circuit between the 153IR and the PW 154.  There have been several OGR threads on how to do this.  For example in this thread ideas are shown ranging from DIY hand-soldered circuits to an off-the-shelf aftermarket module.

In that thread I see I proposed a no-soldering-required solution using off-the-shelf eBay modules for less than $10 (free shipping from Asia).  In the 3 years since that thread additional eBay modules have been introduced that make for an even simpler solution.  I can provide additional info on how to do this if of interest. 

Or, the Dallee 367 module referred to in above thread is apparently still available - $25 (plus shipping).

Yes, yes, please send me all the information you can because I have a whole bunch of post-war 154 signals that I would like to use I grew up with post-war and like using post-war stuff. Really appreciate it

Jerry 

Well, I'd say the fastest way to get up and running is to use an off-the-shelf module like the Dallee 367 module.  I do not have one of these (nor a PW 154), but using their instructions it would be wired something like:

The Dallee 367 appears to be $25 (plus shipping).  There may be similar off-the-shelf flasher circuits.

As suggested earlier, I am a student and devotee of the insanely low-priced eBay modules.  If one is willing to experiment a bit and/or desire re-living your childhood Lego building-block experience, you can implement suitable flasher functionality with just 2 eBay modules for less than $5 out-of-pocket:

You'd hook up the two modules as follows.  This would drop-in to the previous post's diagram to perform the 2-wire to 3-wire flasher-circuit "black box" function.

And here it is in action.  The video shows how the timer module on the right can be "re-programmed" using the buttons to change the on-off timing of the flashing.  

And, yes, that's the relay "clicking" on and off which I suppose may be bothersome depending on where it's mounted and what not.  You can buy or cobble together a "solid-state" no-moving-parts (i.e., "silent") version of this timer module too.

To be absolutely clear, if you're after simple plug-and-play don't try this at home...trade-in your PW 154 for a "modern" 154 which has the built-in flashing circuit.  Or, buy a Dallee 367 or equivalent.