It is a tough one. My 67 GTX has a 68 440 in it also. I bought it for about $11k 16 years ago and probably have well over $30,000 in it now - maybe close to $40k and it could still stand to be painted. Lots of expensive stuff - replaced most of the glass with better glass, replaced a lot (a whole lot) of trim, dyed the interior to freshen up, restored/retextured and dyed most hard plastic. Rebuilt & refinished gages, new Magnum 500s & redlines, rebuilt the transmission with lots of new stuff, All-Trim restored tail panel, grill, tail light bezels, added PB, re-cored radiator, rebuilt AC system and charged with R12, new heater core, new rear and sure grip, rebuilt/restored entire suspension, new brakes front to rear, complete TTI exhaust, hood pad, weatherstripping, etc. A lot of this was before reproduction tail light bezels, consoles and tail panels were introduced so very expensive to restore. With exception of gages and trim restoration I did nearly all the labor myself. And yet it's not really a restored car as the paint is old and the interior upholstery is not up to standards of a new Legendary interior. Considering that I doubt I could get more than $25,000 for it which is pretty much what it appraised for about 15 years ago.