Depends on where you race them.. the Mini T has really brought them to the lime light. In some cases, they are as good or better than a speed 300. The best thing is the aftermarket motors are like the 1/10th counterparts in that you can get replaceble brushes and springs, and retrue the comm (can't on the 300). I think also the mamba will have this mounting (right now its at another but Shawn mentioned this was a oversight).
Im not sure how you are mounting the motors, but depending on the method, you could drill additional holes in the 300 mount. If nothing else, I guess I could find a aluminum aftermarket adapter to fit it in (problem is I have never heard of one). But you might turn away buyers with this oversight.
**The 180 top mount might still be doable with the 280 as it isnt that much more weight versus the 300**