I obviously have a vested interest in selling a car but putting my impartial hat on here I would buy one that has been unmolested and have it done as you want by the garage you want. At least then you have the peace of mind of knowing what was done, by whom and when etc.
And, with good quality cars being available at lower prices and parts coming down in price, it makes financial sense too.
[Now the sales plug ]
I have a superb 1996 GZ for sale that has a FSH since 1999 and I am willing to bring it half way to you to show the car. If you bought that and put a single conversion on, it would cost you in total much less than most single turbo cars are being advertised for. And you can have it now and be singled before Xmas