Thought I'd post this as it might of interest to TXT-1 owners out there (and possibly TXT-02 and Jugg owners too).
I recently bought an EzRun 4274 combo from Ebay, to fit either in my TXT-1 or the half track I'm building (In the big rigs forum). I did a trial fitment in the TXT-1 and with the aid of a home made spacer it fits quite well:
Before and after, the 2 Trinity chameleon motors for size comparison against the 4274. The 4274 also has an extra 4mm on the diameter:
I used a RW racing pinion, and 15tooth for 5mm shaft. It was a bit of a tight fit, but running a 5mm drill bit through the centre removed the slight high spots around the grub screw hole and now it slides on smoothly. It also has the advantage over the pinions on the standard size motors of having wider teeth which match the counter gear width perfectly.
Spacer is clearly visible here. It's made from a 5mm thick aluminium plate, and gives perfect separation for fitment of the pinion. It's circular, 40mm diameter, 14mm centre hole, with motor holes 25mm apart.
Fits in the chassis quite nicely:
Although it is a very close fit to the suspension cantilever.
If I'm going to fit it I still need to cut a couple of pieces out of the spacer plate to accommodate the countersunk screw that holds the centre counter gear shaft, and also the bottom mounting screw closest to the motor, but it's a fairly simple fitment to fit what is a motor that is quite larger than normal. The motor is only 2000KV, but the combo is rated for 4S, which would make the performance quite lively, although I would probably only use it with 3S at the most.
Still can't decide whether to put it in this or the half track though....