Is this the hull you ordered?
http://www.imex-model.com/product/TA...IS.html?cid=90
To answer your original question, if it is the hull, then these will fit for sure without modification
http://www.imex-model.com/product/TA...29.html?cid=90
but for scale speed you want the 4 shaft
http://www.imex-model.com/product/TA...29.html?cid=90
and I believe to use them you have to move the smoke unit. Erik will know for sure. Either way, in my opinion, unless you can find a set of asiatam dual ratio brass gearboxes then these are the best deal on the market today. They're the state of the art for stamped steel-sided gearboxes and they're at the last version's price (for now). I've already ordered two pairs myself and if I had the coin I'd get about a dozen more before the price goes up. As it is I'll keep trying to pick them up one and two at a time as soon as I can, because I think it's going to be a while before anyone comes out with anything better, or for a better price.
There are other gearboxes on the market with all-bearings and pretty colored motors but with you being in NY that means $8.99 for shipping so I don't think you'll find a better deal. These things are seriously robust and have plenty of power. A guy I know drove a pair through a pile of laundry (why, I have NO idea) and when he powered through the towel in the sprocket the gearboxes took the punishment and actually tore the idler right off the back of the tank. And it was a full metal tank.
Hope that helps, and remember, PICTURES, Bro.
Gary