Battery hold down question

Hello- I am about to replace the battery in my '71 Mach 1 429, obtained a number of years ago from the esteemed Mike Berardi. I need to install a complete battery hold down assembly as there is none currently. I see a number of those hold down parts on the NPD site, among others. Open to other suggestions as far as purchasing it. However there is nothing other than a square hole where the hold down would attach to the inner fender liner. Any thoughts on the best place to obtain this part?

Also, the under hood area is very clean overall, but there is a little corrosion on one end of the battery tray, which is otherwise solid. Thinking I should just scuff that section up a little bit and apply something like POR-15. Thanks

Originally there would have been a nut inserted in that square. Most I've seen have long since disappeared. You can buy a caged nut ( https://www.amkproducts.com/bulk-fasteners-listing/?codeforlookup=7125 ) and stick it in there, just be careful not to lose it when you remove the bolt. Alternatively, you can reach up under the fender opening and hold a nut while running a bolt in from the engine side or, if you have the ability, weld a nut in place.

I like to use VHT Chassis and Rollbar paint for under hood touch up.

My car was also missing the captive nut in the apron. I used a caged nut as Sheriff41 suggests. Got a package of 4 off eBay for a few bucks. Worked fine. I recently replaced the hold-down J-bolts and the bracket. Got both from NPD. No issues. I used my original plastic hold-down bracket. I suspect the repro part would do just as well.

For engine bay paint, I've always used satin black Krylon spray paint. Grind away the rust, shoot some black spray primer, then top coat.

Thanks for the responses guys. I wasn't sure if there was a Ford part number for this piece, and it sounds like the caged nut will do the trick. What size did you go with? It also looked like the J-bolts on NPD are taller than original but I'll have to read that again. I just have a slight bit of corrosion in the right side of the tray and was hoping to clean it up a little and then brush something on. Might go the spray route however per your suggestions.

After looking at many batteries I went with the Everstart Maxx 24F. Has a nice flat top which might take a topper. My car is a J-code but when it was restored it doesn't appear that the larger tray was used that will hold a 27F battery.