Rover produced two main P5 types;

the 3 Litre Straight Six, known as a P5 and the 3.5 Litre V8 known as the P5B

Both of these models were available in a choice of Saloon or Coupe, the latter being the most desirable.

The P5 (3 Litre) had an option of a manual with overdrive or automatic gearbox.
The P5B (3.5 Litre) was only available as an automatic.

Visual Differences

The easiest way to differentiate between the two models would be the wheels, which on the P5B are Chromed Rostyles.

Other points to note would be side indicators, no hole in the front grille for the starting handle, rubber strips to the over-riders and recessed fog lamps to the front wings - all found on the P5B and not the P5.