You really need to speak to Jim Key, Custom replicas headboy.
He has built both versions.
Basically the Engle kit is a rough approximation of the Disney nautilus. Close one eye and stand on one leg, about 10 foot away and it looks pretty authentic, other than that it is lacking in detail (very low rivet count!) and the shape isn't right. If you're a purist, then this isn't the boat for you.
The kit comes with all the dive/ballast equipment and pressure hull, although you will need to make some alterations to the basic design to get a good working model- I'm sure Jim will point out these if you ask nicely.
I don't think Custom Replicas make a kit as such, they will supply you with a commissioned piece built to your requirements though.
Their model is a faithful replica of the Nautilus, built to the Studio blueprints (which actually aren't 100% faithful, but I'm splitting hairs here) and if the photo's are to be believed is an absolute work of art.
Not cheap mind- about $2000 I think for a basic version! How deep are your pockets?
You may also want to have a word with Bob Martin, he has some nice 1/32nd castings that are probably a lot less expensive than the Custom replica versions.