Off the top of my head, and because I can't be bothered looking up exact dates right now, it looks roughly like this:
2000 single carb manual. Right from day one (late 1963)
This was joined in 1966 by the 2000TC (twin carb, manual box only)
and the 2000 automatic. (single carb only)
The V8 was launched in early 1968 in automatic form only.
These are all series 1 cars, identifiable by the aluminium grille and flat bonnet. The only body panel that changed significantly was the front valance.
Series 2 cars were launched in late 1970. Identified by the black plastic grille, power bulges and badge on the new bonnet, vinyl rear pillars and black or brown sills. Models were as before:
2000SC manual, 2000SC auto, 2000TC manual and V8 auto.
Late 1971 saw the launch of the 3500S manual. Basically the same as the auto but came standard with a vinyl roof, ambla upholstery and different hubcaps.
Late 1973 saw the 4 cylinder models upgraded to 2200 but keeping the same 3 models. The 2200s also had a few upgrades under the skin which gave them more in common with the V8s.
Oddities: Rover sold reasonably well in the USA in the early years (from 1964) and while the early cars were basically just lhd versions, later ones became more tailored the US regulations so the 4 cyls were suitably blinged up with extra trim, special colours, funky wheels and such and from 1968, extra lights and complicated dual circuit brakes. Some of the features also made their way onto some European export models. USA cars are known as NADA or Federal models.
Rover launched a special 3500S auto version for the US market from 1969-1971. This was everything Rover thought the Americans wanted and featured triple bonnet scoops, larger bumpers, electric windows, power steering, often air con and a host of exotic extras not seen anywhere else. It wasn't a success and only a couple of thousand were built.
Estates: FLM panelcraft were licenced to build estate conversions on the P6 from 1969. It could be done to a new or used model and somewhere around 200 were built (no-one knows for sure) The conversion wasn't that well done in terms of rust prevention so the survival rate is low and many Estate bits have been swapped onto replacement base units.
VIP: Rover built a special edition towards the end of production in 1976. Available in either brasilia brown or platinum silver they featured a brown vinyl roof and pillars, special brown velour interior, air con and pretty much every option available at the time. Only 77 were built.
Convertible: There was one convertible commissioned by Rover in 1965 as a prototype, built by FLM panelcraft and still around today.
Graber: Swiss coachbuilder Graber built a few conversions on the P6. Starting with his own 2 door convertible in 1965 (prettier than Rover's) then followed by 3 2000TC 2-door coupes and a V8 2 door coupe. All are gorgeous, the convert and 2 of the 2000 coupes still survive, the others are MIA.
Zagato: Another one-off coachbuilt effort/styling exercise. Based on a 2000 TC but radically reskinned to look more like a contemporary Lancia. Still around today.
I think that's the main ones. There were some 4 pot rally cars and the bulging, musclebound V8 racers. Other famous cars are mostly per-production examples and of course the grand-daddy of them all, the Rover T4 gas turbine prototype.