I know of the Jaguar set, but is there another interior I can use for a stug III B driver's compartment? Would one for a pz.III work?

Eduard.

http://www.eduard.com/store/Eduard/StuG-III-Ausf-B-interior-1-35.html?cur=1&listtype=search&searchparam=stug

This only works with the Tamiya StuG B and misses final drive, gearbox etc. It does not work with the Dragon B.
Not shure for what reason you´d need a drivers compartment on these Stugs. If I´m not wrong abot the Tamiya upper hull, none of these two kits could exhibit a drivers compartment without the help of a saw.

For a complete interior with the Dragon kit (wich is compared to Tamiya crap anyway...), you´re pretty much doomed to use the Jaguar kit, or take another set for another Stug or Panzer III and scratch what´s differnt or missing... which is quite some work. Interiors for F or at least G are more than a bit differnt.

I think the way the engine or gear box was mounted, was changed on the later Stugs, but the B could also been the first with later alingement. Sadly I can´t look that up right now.
If you only want to show the final drive through the front glacis hatsches, I think you could use about any Panzer III or StuG III interior set, it might not be accurate to the last rivet, but not really noticeable. As soon as you want more than that, it would be best to go with Tamiya and Eduard for the fighting compartment and another Pz. III or StuG III interior for the front part of the vehicle.

Matt never said which kit he is building Dragon or Tamiya?

I will be building the Tamiya kit. I know of the Eduard set, but didn't think that would include the transmission. I was considering removing the front upper hull.

Fabian: I have read the reviews and it appears to be a difference of soft spots. I may kit bash the two.

I'm a building this for a friend. She wants to give it to her sons, who I am hoping will become interested in the hobby.

Ok, it´s the certainly the easier solution. Just had a look, you can open those hatches on the Tamiya kit.
As said, you might have a look at one of the other interior sets around. Use the front and keep the rest for another chance. If you going for the removable roof thing, you should go for the Eduard set aswell. The Tamiya interior on it´s own is a bit basic, but enough to place a figure in the hatch.

Well, speaking of the comparing the two kits... as having the Tamiya kit in the stash and the Dragon (at least kind of) build, I might add a few sentences.
(I´ve build the Wittman Ausf. A, which is basicially the same kit with about 5 extra parts.)
Dragon is said to be more accurate in the dimensions, but has some (or a lot?) wrong details.
I´m not too keen on having the the glacis plate matching plans down to the quater of a millimeter, while the roof features bolts instead of screws, the gun is missing the characteristic weldseam on the "collar", having a ridiculously simplified smoke discharger, pretty off weldlines and so on. Shure the tracks are better than the rubber ones Tamiya offers, but that´s it. If you´d build it ooB, not all could tell whether it´s a Tamiya kit from the 70ties with aftermarket tracks of not.
Bashing those two dosen´t make nuch sense I guess. On every part the dimesions are correct, some detail is wrong. You can´t use the roof (because of the bolts), the fenders aren´t worth the transplantation, there are way better ones out there. Lower hull from Tamiya might be better aswell, not speaking of the weldlines Dragon offers... Better get some replacement tracks and leave the Drogon kit out.

The tracks are the main reason for bashing the two. The roof will be replaced with a canvas cover over it. I have built the Tamiya kit, before. It's an easy build. Again, the reason for the interior is to draw attention to the possibilities available, in this hobby. The Dragon kit goes for $20. I don't think that is too absurd.

Ok, if you can geet it that cheap... even aftermaket tracks would be more expensive here.
Well... I can´t prevent you from replacing the upper hull. But again, I wouldn´t recomend it. Shure you can replace the Bolts with screws (as I have done it) or throw a carvans all over it... but why? There isn´t much detail which is better than on the Tamiya kit, the better dimensions aren´t that much help if you gonna hide them anyway...
Btw: I think the roof of the early stugs is the perfect place for showing some color modulation. There aren´t many panzergrey subjects out there which provide such a big playground.
In any way, I´d be interrested in you build, wether with Dragon upper hull, or without.