If I found an all original matching numbers documented Sandman I would restore it exactly as per original..... that is what a restored car should be and to me is worth the most money.

As far as I am concerned those who say it is about the car not the money are talking crap. No one likes to lose money and at a minimum want to break even if they have to sell the car. There is something wrong with you if you spend 60K restoring a car and think nothing of it if you only get 40K for it when and if you have to sell it.......

If you don't have documented evidence of an original engine fitted I don't think it devalues the car too much if you fit an L31 M21 combo to an original L20/L32 M20 car as long as it is period correct.

For me.... non factory original colour and trim devalues the car by at least the cost of returning it to original factory colours.... just rubbing back the car and repainting it the factory colour would not be good enough for me as a restored car should be painted as per original and not one or two different layers of colour.... the car would have to be stripped, taken back to bare metal and sprayed it's correct colour so definately no change out of $10,000.

An incorrect trim colour is also not cheap to change back.... the interior and complete dash has to be removed and re-installed..... if the original colour was Buckskin and had been re-done in black the crashpad has to be re-skinned... $450.... new door trims.. $900... seats and console pad recovered... $1000... new carpet.. $250... new headlining and visors.. $300 ... strip all the dash and console back to bare plastic and have it all repainted... $400??? door armrests re-skinned.. $300 .... so at least $3600 to restore the interior trim back to original.

Your $40,000 Sandman with non-factory paint and trim to me is now only worth $25,000 or less.

Personal choice of the potential purchaser also plays a big part in value particularly with colours. I much prefer the bright 70's solid colours over metallics and particularly dark metallics...... I would pay more for a Jamacia lime HJ than I would for exactly the same car in Jade green. I would pay less for one with a Tan or Chestnut interior.

I don't think fitting optional extra's like power steering and factory air would de-value a car but I don't think it necessarily increases the value either as many people know these were rarly optioned on Sandman or GTS for that matter as they were very expensive options in their day...