Where could a novice read and learn more about Jaguar autos i.e. XJ6 and
XJS?

Interested in viewing year to year photos of the cars to spot differences in
styling from model year to model year (i.e. 1989 4 round headlights, 1990
square headlights???)

1)  What are the differences betweeen XJS and XJS Sovereign?

2)  Were the XJS's dependable cars?  How was the roadster?

3)  What other achilles heels (besides rust) should one look for in test
driving/examining a car for possible purchase?

Thanks!