I didn't think the boxed Chevy frame would flex as much as the old Ford frames did. But the 50 Studebaker had the same type of boxed frame as the Chevy and that twisted a lot when you jacked up a rear corner
My son still has his 41 Chevy but it's been off the road for a while. He thought it would be fun to catch some air at a railroad crossing that was about a foot higher than the road. He did it all the time on his motorcycle. It didn't go so well for the Chevy. The driveshaft was a little too short and didn't slide back in when he came down. it snapped the transmission off at the bellhousing and broke the spring perches off the rear axle and rotated the axle 90 degrees. It's been out behind my garage since. He fixed the axle but used the engine in a Camaro that he sold. The frame came through it ok. I just checked it for cracks and didn't find any.
We used 1/4 inch plate about a foot long on the top and bottom and 8 in long on the sides to stagger the welds. It wasn't a very difficult job but if we were doing it again we wouldn't do it. The Nova parts are already obsolete and are expensive now if you can find them. We would use a Fiero IFS front crossmember attached to the stock frame. Then 20 years or so down the road it can be replaced with something up to date and still have a solid original frame.
What do you think Don?
AL