Welcome to the forums!
You'll have to modify the chassis tranny hole a tad with a dremel or file. Go slowly taking just a tiny bit off at a time test-fitting the tranny every few minutes. Then, the mounting holes in the chassis will have to be elongated a little to match up with the E tranny.
To lock in second, you can either do a homemade job where you screw the dog carrier into second gear, or get the gmaxx locking hub:
You are most likely going to want to get the following as well:
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Steel idler
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Strobe slipper setup
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Ofna 51T spur
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Mod1 5mm bore pinions assuming you go with an XL motor. (10th item down the page).
Revo centers might fit, but they may rub a little on the Revo bulks. A little dremeling should fix that. Or, contact Mike (site owner) and see about getting custom dogbones made.