The "Rule of Thumb" tends to be that you NEVER get back what you put into a restoration either stock or restomod. Maybe 50 cents on the dollar if you're lucky. The finished product may be priceless to the owner, but not to potential buyers. Your query asks for a tangible answer to an intangible question. You'll get opinions, but no definitive answers, and as they say, "Opinions are like belly buttons. Everybody has one.". Soooooo, while it's a thought and debate provoking question, there is no answer. You're comparing unequals with too many variables. In reference to the V8 Zs in the pictures above, the real answer to your question is that they may or may not be worth more than a nicely restored early Z. It's in the eye, and wallet, of the beholder. Dennis