Charlie, without speaking to rating, I think the course will play 3-4 shots harder for three reasons.
First, hazards off of the tee are now in a position to catch a good drive that is offline. Before, a well struck drive cleared most first shot hazards. So now, you duff a drive, you can recover, but with a longer second. Which brings us to the second reason.
The greenside bunkering is deeper and the entire green complexes now function as units, as they did originally. So a miss on an approach is probably a stroke. Greens are 20-30 percent larger, and that brings us to reason three (or maybe reason 2.5).
A missed approach could still be a green in regulation, but just hopelessly out of position so that a two putt is a challenge.
These three reasons have nothing to do with the length of the holes. From the restored championship tees, the course will measure approx 7,200 yards, par 70. Good luck back there.