Not sure what "frame" connectors are but subframe connector is the terminology used when discussing unibody cars. I didn't actually start attending drag races until around 1970 but I definitely had my nose in the car rags in the mid 60's, thinking there probably weren't a lot of unibody cars in jr-stock, now if there was a car that should have used subframe connectors it was Jenkins' 66 Nova as it was (one of) the dominant cars in A/S, the other car would have been Jere Stahls' 66 Hemi Belvedere car, not sure NHRA would have allowed them though.