Does NASA accept grandfathered SCCA logbooks?
Rally cars with SCCA logbooks have certainly run at NRS events in the past, but it's a little more nuanced than that.
NRS doesn't "accept" any logbook as a magical "you're allowed to race this car" passport. That's true even for the logbooks that we issue ourselves. What our rules talk about is reciprocity with other organizations, not with a logbook itself.
As of 2020, NRS accepts the standards from ARA in the USA, and CARS in Canada. That means if you have a car that's legal to run under them, and a logbook accepted by them, when you show up to a NRS event, you can elect to have your car tech'd according to their rules, and if it passes, you are eligible to compete.
Example: you have an ARA-legal car with an ARA issued logbook. You arrive at a NRS rally and say "It's ARA legal, please tech it according to ARA standards". It passes, super, you can go race. Note that all of this is discussing "eligible to race" issues, not "which class does it compete in" issues, which is a separate thing entirely.
Where does SCCA fit into this? NRS has never had reciprocity with SCCA because they got out of rally around the same time NRS was formed. Rally America, however, took over managing SCCA rules and handling the grandfathering of all those cars. So when a SCCA car showed up at a NRS event, the process was actually "please tech this car according to the Rally America rules", and those RA rules including what was and wasn't allowed as far as handling older cars with SCCA logbooks. In the RA rule book, there was a section explicitly detailing that grandfathering.
In 2020, ARA's rules do say they accept SCCA logbooks, but there is no section on grandfathering, instead there is a clause saying all cars must meet ARA specs. This means that a car competing at an ARA event, with an SCCA logbook, has to meet the specs listed in ARA rule book.
Similarly, a car with an SCCA logbook can come to a NRS event, and if it's not already NRS- compliant can ask to be tech'd according to ARA rules.
So if your car is not compliant under the NRS rule set, and you want to know if it can be grandfathered with an old SCCA logbook, what you need to do is find out whether it is current legal under ARA or CARS. If your particular situation requires detailed discussions with those organizations, make sure to get those to your NRS tech well before the event.
More explicitly, NRS has never had any rules allowing grandfathering of old SCCA builds. The many times those cars ran with us, it was always via a "running under another rule set" procedure.