classic - engine swop to diesel

How does this affect the value of a car, i saw a 95 model which started life as a v8 manual and is now a 300tdi auto,

the car was at a dealer, a LR specialist, but it had no paperwork. to me it looked well done and it drove nicely.

What discount versus a factory original should i expect ?
Best Regards
Rick

In my view the dealer has increased the value by fitting a 300 tdi engine. The only snag being that your insurance company may demand an engineers report to say that the modifications comply with the manufacturers specifications and that the vehicle is safe.

thx mike, will check with insurance people