I agree with Mike, go to the NHRAracer.com website for access to the rulebook, not the regular NHRA page. They usually sell actual paper copies of the rulebook too, although I don’t see it offered on there at the moment, maybe because it’s so late in the year. They usually have actual copies of the rulebook for sale in the NHRA merchandise tent at national events too. NHRA does have a cheat sheet of sorts, I posted a couple example pictures below, although be aware, I’m sorry it’s 10 years old, so stuff like the helmet specs are out of date. I’ll have to look around to see if I have a newer version. I think they include these sometimes with the membership packs.
That NHRAracer website also has a section of NHRA accepted products, be sure to check that out too. There are lots of products, even sold at places like Summit, Jegs, etc., that although might be functionality fine, may not be NHRA legal, or legal at a certain ET, etc.
Along with the rule book I’d advise going to any drag strip you have nearby and check out some cars, especially if you can find any similar Mustangs, and talk to the owners, see what tips they have. Bigger races the better possibly, just for more cars to check. The cage diagrams in the rule book can be kind of generic, sometimes a specific vehicle can have particular challenges where you have to get creative, but stay within the rules. Often times you can see alternative ways to do something, and still be within the rules. Be aware too that occasionally track tech inspectors don’t always give accurate info, don’t be afraid to double check something with another source.
I’d say to go back and check through Jay Brown’s various “Road to Drag Week” posts on the website here, he has lots of info & pictures from when he built his various Drag Week cars in the past, including the cages.
And if Hot Rod Drag Week, or any of the other Drag & Drive events that have sprung up are running near you try to check them out too, although their stops at each track are brief, and drivers take off early and hit the road often. The Hot Rod Drag Week rules can sometimes be hard to interpret, and even among participants there is sometimes disagreement on what’s allowed as far as Hot Rod’s build guidelines for a particular class. And unfortunately Hot Rod is notoriously hard to get ahold of for clarification. Hot Rod has also been doing 3 year rule sets, I’ve lost track of where they are in the current set, but that’s important to check, so you don’t build your car to a current spec that changes in the (near) future. Many people have started a build that takes longer than planned, and wind up no longer within the rules of the class they intended. Best advice is usually to build the car you want, and let it fall into whatever class it winds up in, but if your goal is to try and win or place in a particular class than obviously more attention needs to placed on that.
There are good chassis shops around that can install a custom cage, and make sure you have a solid foundation, if you decide you want to go that route, you can possibly get recommendations here or at your local track for someone near you.
There are a few Facebook pages for Drag & Drive events, although some don’t let you join until you’ve actually done or entered an event, but they can sometimes be good for clarification on the various event rules, by people that have “been there, done that”, although beware again, there is often disagreement on what’s ok, but occasionally you can get the right person’s attention. I’ve also found the advice many people on the internet give out about what is & isn’t NHRA legal is wrong, or misinformed, more often than not it seems.
Keep asking questions as you think of them.