Don`t know if this helps as I`m modelling the late 50s and the track would be different in the 70s, but I`ve been looking closely at OO trackwork and decided to go with C&L, I`ve made a few of their point kits and I think its the best option at the moment, for flexi track I looked at C&L, tillig, SMP and exactoscale (track base).
The problem with OO is that if you go for the correct scale sleepers per 60ft it looks wrong looking more like narrow gauge track, C&L flexi works out at 26 sleepers per 23cm (60ft at 4mm/ft should have max 26 sleepers per 24cm) so I settled for the following for my straight track;
cutting the flexitrack into 23cm sections
soldering droppers to each rail
glueing to 48mm x 4mm cork strip off centre by 4mm for the ballast shoulder (for double straight sections gives approx 45mm track centres)
removing the web
spraying with sleeper grime/rust
then dry ballasting
then going to the baseboard
drilling holes for the droppers
then connecting each section like set track using exactoscale fishplates before glueing the cork down and then dry ballasting over the gaps and finally airbrushing for dirty ballast.
Takes a while