Welcome to digitalcorvettes, Clay. The value is not so much the year of the interior/exterior combination as it is the overall quality. If you are going to drive and enjoy it, there shouldn't be a problem. If you want to turn it into a points winner at a resto show, yes it would matter. A big question is why it was re-bodied. Was it because of a wreck or fire? or did a previous owner just up grade the front and rear facia. If the cowl section was replaced, did the VIN change? Was it a '79 with a new frame or a '75 with '79 body pieces.
If the title is good and you are happy with the Vette, Don't be afraid of it. Jus be aware of what you are getting.
I don't know if it would affect the value as long as it was done right... I paid $7000 for my 75 that had a rebuilt engine & new paint. All it needs is seat covers, carpet & weatherstripping.
From what I have seen the later C3's prices don't seem to be all that affected by mods, I have seen them with sidepipes, different seats, different engines, spoilers, etc... and all roughly the same price as original cars.
The value of this vehiclew is strictly from an enjoyment viewpoint. What is it worth to the buyer to have the driving experience?
That is what it is worth.
The fact that the body has been replaced will effect the price on a lower scale. This vehicle will never be a collectible vehicle not that it would if it was original. It is strictly a driver.
Why was it replaced and how well was the job done? Has Bubba been there? Is the body stolen? How am I going to sell this in the future?
These questions will come up everytime the vehicle is sold. Why take the chance when there are plenty of cars out there without these issues? Only a big reduction in price will make it worth while for somebody to take that risky a leap.