As long as everything is done right I wouldn't be worried. They are old cars at the end of the day.
My father in law has just rebuilt an xk120 jag if you'd have seen it when he bought it you'd never believe it. Since then he has won numerous concours shows with it.
With regards to service books as long as there is history of recent work what's it matter about whether it missed a service in 1989!
If it's been restored most stuff will have been replaced in anycase.