Hi Chris
For concrete track its worth looking at the stuff exactoscale sell.
This is the P4 version but its available in EM and OO via Intercity models. It takes peco code 83 rail which is the right height for 4mm scale, code 75 is OK for HO which is what OO track actually is but in side on views it looks too small and you cant see the gauge discrepancy from that angle.
HTH
Jim
For concrete track its worth looking at the stuff exactoscale sell.

This is the P4 version but its available in EM and OO via Intercity models. It takes peco code 83 rail which is the right height for 4mm scale, code 75 is OK for HO which is what OO track actually is but in side on views it looks too small and you cant see the gauge discrepancy from that angle.
HTH
Jim