Brian, I've been following this thread with great interest and when it comes to frames I'm not as well versed as you and or many other people here. I just felt that I needed to mention a situation that I ran across in the past to get proper gaps and sheet metal alignment.
The shop I was at had a Camaro with a similar situation due to a collision. We where working with a new replacement GM sub-frame and when installed to the measured tolerances, we couldn't get the sheet metal to line up. The car had been hit (and fairly hard for insurance to pay for a new sub-frame) so hard in the front end that it changed the dimensions on the rear frame slightly, it was a while ago but I think I remember one side being out 3/16 inch compared to the other. Door gaps where moderately acceptable but the rad support, fender and hood wouldn't line up at all. Our frame guy pulled the rear frame, we had much better gaps and all sheet metal fit.
It was mentioned that this Nova was hit, could the same situation be the problem here? I know that if your measuring from what's supposed to be a constant position and that position isn't constant anymore, a 3/16 of an inch towards the rear of the car can mean an inch or more on the front especially when dealing with 2 seperate frames on a vehicle.
If I'm way out to lunch let me know, as I mentioned in past posts, I'm here to learn more.