Honestly it depends on how much you can actually do yourself restoring the '68. Labor cost is what racks up the $ on restores, especially metal fab and replacement.
However, if you're paying someone to fix up the '68? There's an old saying - the cheapest way to restore an old car is to buy one...
If you want to see some results where cars actually sold - check out Cars and Bids. Buddy of mine was up late one night with a few (maybe more than a few) drinks in him and he bid on a car. Went to bed thinking, I'll never get it for that bid. He did. Prices are reasonable most times and seller...