Currently looking at 54 cm Tarmac and 54 cm RoadRacer <-- thats about correct... your saddle height will be around 71 to 72ish cms. Stem sure will be between 10.5 and 11.5.

Technically IMO you should go with anything aroundish 54 to 55ish virtual top tube.

How the bike will feel in long rides will depend on your setup, some bikes are better at it anyways but it will depends from the set up you did to the bike aswell.

I have a bmc and no problems in long rides, but i wouldnt use an aluminum stem and handlebar on it.