Basically when using the hand in option

you'll always see <class> <lvl> <item> 0/24, and it actually changes each phases so some can be as low as 16, while highest i've seen so far is 58-60 (but that's on later airship parts)

but it sounds about right what you said with your classes requirement. But again i must stress, it changes after each phase, and you have a total of 12 phases (4 airship parts with 3 phases each)