It depends!
What it comes down to is your budget and how you want to use the machine.
Is it going to be a show piece? Or will it be put to use?
In either case, you will need a new outer cloth bag, bag top wire, and bag top cover, since the cloth F&G conversion bag you have probably won't fit any of the genuine Kirby parts. I say probably because you might be able to get it to fit, but it's highly unlikely.
If it's going to be put on display, I'd recommend using the dump bag system since it's a bit cheaper but still looks very nice. The dump (or shakeout) bag system has a short zipper near the middle of the cloth bag, with no disposable paper bag inside.
If it's going to be put to work, I'd recommend using the disposable dirt bag system. This will require the full-length zipper bag, mini-emptor, fill tube, and a fill tube adapter - 'F' style or otherwise - plus the disposable dirt bag inside the outer cloth bag.
The dirt bag can be either paper or cloth HEPA, but I'd recommend the HEPA bags since no one likes to breathe vacuum-agitated dust. Kirby makes wonderful HEPA-filtration dirt bags, though there are cheap ones on Amazon if that's a concern. Personally, I like genuine and have never had an issue with Kirby bags.
The other, absolute bare-bones option is to just get the fill tube and fill tube adapter, then zip tie the fill tube to the end of the F&G nozzle at the bottom of the existing bag. That way you change literally nothing on the machine and get the ability to use Kirby bags in it again, for next to nothing. It's not great, but it works!