I know its not really a retro car yet but it is close, the first Rover 820 was available in 1986, mine is a 1994 model. I have owned four and really like the old barges.
I bought this as a standard and very good condition car at 6 years old with about 80,000 miles on the clock and its been brilliant, then I fell into the trap of making a few changes, then a few more and now its become a time and money pit like I suspect most of the cars on here.
This is the car soon after I bought it
About a year in, lowered all round and exhaust replaced.
About 3 years later, lowered some more, 6 spoke sport wheels, and cooling for the intercooler through the front bumper.
This is the current engine.
This was taken March 2015
A short video taken spring 2015.
Probably not everyone's cup of tea but its my pride and joy.