Having owned three of these cars, I strongly recommend buying one from a knowledgeable Silver Shadow II owner or used RR/Bentley dealer. Excellent, well-kept models are hard to find, so you may have to look for a while (it took me almost six months to locate the near-perfect example I have in my garage now).
As for the best versions of the Shadow, definitely stick with a post-1972 model with the 6.7 litre engine, revised dashboard, and non-metallic ("non-pan-scrubber") compliant suspension. The very best versions, in my humble view, are the Shadow Series II. These have enhanced front and rear suspension, rack-and-pinion variable assist steering, much better road manners with less front tire toe-in and under-steer, far less gremlin-prone brakes, and the impressive RR split level climate control system.
The Series II was built between 1977 and 1980 (the Silver Wraith II is identical except it is the LWB version, about 4" longer, with a vinyl roof). Finding one is not a problem... finding a GOOD ONE is a major issue. Do not skimp. It is worth paying in the region of $22,000-$28,000 for a well-maintained vehicle than being tempted by a cheaper, older Series I model.
They are all wonderful to own and drive, BUT they can be very expensive to put right if they have been inadequately serviced and maintained. So pay that $80-$100/hour to a trained RR/Bentley service tech. to give your prospective purchase the once-over: Best money you can spend ahead of a used RR purchase. Good luck.
The car (esp. the Shadow Series II and Wraith Series II) is magnificent. It looks right, drives right, and holds its value right. But these cars are getting old, so don't buy a "doer upper". You'll get depressed and go broke trying to bring it up to grade... and ultimately spend far in excess of what you would have spent if you'd bought a good one to start with!
Dr. Mark T. Motte (RIMOTTES@AOL.COM)
I just purchased my first Rolls. It is a 1978 Shadow II. It obviously has been setting a while and needs some TLC. The fuel is old, the battery dead. The interior trim was sprayed painted in a lame attempt to improve its appearance. The trunk floor is pretty rusty too. I purchased this car without driving it first. I have absolutely no regrets. Jump starting the car brought the engine to life. The engine was smooth and quiet. The gear selector contacts do need cleaning, as finding the right gear is a little tricky. I found drive, checked the brakes, then pulled out on the road for a quick three block trip to the golden arches and back. The look over the bonnet was amazing! The ride was spectacular. It sputtered a little in protest of the old, rotten fuel, but smoothed out again and brought me back to my garage. It is a keeper. I found the complete workshop and parts books on eBay in CD form. I am looking forward to giving this car it's dignity back. It will repay the favor ten fold.