SS/B and SS/A Chassis and Suspension

From looking at old photo's the Prostock class new for 70 the cars were modified
heavily from the beginning of the class. All the tricks you are asking about and more.
The SS cars that remained in Super Stock were left alone at least up till 71 from what I
have seen or have proof of in old publications.
It may help to get a nhra rule book for the age you are wanting to know about.
As you know I am building my project to the 73-74 racing years.
This is what the 1973 nhra rule book states about roll bars in the super stock class:
Required in ALL convertibles in Super Stock classes.
Recommended in all Super Stocks.
Roll cages permitted in Super Stock provided additional frame members or cross
members are not utilized.

For 1974 the rules are the same as 73 with exception of the (provided additional frame
members or cross members are not utilized) was not included.
So It reads to me frame connectors were first allowed in Super Stock for the 74 season.