Lionel electric rr in older engine

Nope.  Jon Z. posted in some detail about the issues with Pulmore motors and cruise control.  Lionel fooled around with it for some time and never got a satisfactory solution.

Bite the bullet and get a DC motor conversion from Frank Timko for the locomotive.

Among other issues, just the field or just the armature wired to the cruise is too much current demanded - very low resistance. The armature and field are designed to be connected in series for the operating voltages we use.

This can be done with a bridge rectifier on the field or the armature in series with the other for DC reversing, but electronic control is still a high current affair and the feedback for cruise is just not there for it to work right.

Try for your own satisfaction running just the motor with a bridge rectifier on the field or the armature in series with the other and a DC power pack with an ammeter. You will get a feel for the limitations of the setup.

What ADCX Rob said, and, I think it might run in only one direction.

I think the easier path is to give up on cruise control and install an AC Commander.

Wired as above, the motor will change direction with the polarity of the DC input.

Rob is right, but I still don't think it'll work properly with the Cruise Commander.  There's a thread somewhere on the board where Jon Z. talks about the attempt to build cruise for AC motors.

I thought Jon was trying to cruise control as an AC motor, not convert to DC and than control.  Though I still think it would be an issue as others have stated.  G

That's correct GGG, but if you recall the discussion, various approaches were tried before they decided that it wasn't practical.  The bottom line ended up being you won't have decent cruise control on an AC powered locomotive.