As rootboy suggested, please post some photos.

Plastic Simplex parts may well be the era of your bike. A lot more bikes had all the plastic Simplex parts stripped off than added....

So, I'd guess your bike probably had plastic Simplex all around. Does the rear derailleur have a "Claw"?

As far as cranks, it would not be surprising to have found steel cotter type cranks on the bike.

Mafac brakes or levers would be appropriate, or possibly Weinmann center pulls.

I think Gitane used 27" wheels on the low end 70's era bikes imported to the USA.

Reynolds 531 is interesting... if it is true. Again detailed photos may help.