For a cage like that any potential buyer will want to know if it has a current NHRA certification, and how long it’s still good for. There would be a chassis certification sticker on the cage. If the certification has expired, how long ago? Cage certification rules can change, if it’s been out of date for a while it may need additional work for someone to bring into current spec for example. Who did the cage? Who did the chassis work? If it was a well known shop that is good information to help sell, and they may have records to help document the work done.
For a race car with that ET potential there will be a lot of components that have/and/or require SFI specs, some of which will have to be within date. Some components might be out of date or need recertification every 2-5 years, so things can be out of date in a short time if it’s been a while since built or last used. The more of that you can document the better. It can be tough for someone not familiar with the various NHRA rules to know what to look for, maybe you can get local racers to give it a look over? Not every potential buyer will care about SFI requirements, but many will, and that can be the difference between a higher selling price, or a garage sale.
Just like any sale of a specialty vehicle like this, it will just depend on how much work someone wants to put into getting it ready to sell, and a person has to decide if it’s worth investing any additional $ into preparing for that, possibly paying an expert to go over it, or just sell as-is, and know you might be leaving something on the table.