Well, I had hoped to dive in to some FPV conversion today, but I ordered the wrong antennas. So now the right ones are on their way, and I opted for the Hobbywing Axe R3 / 4274-2000kv upgrade instead.
I recorded the whole thing, if anyone is interested I can edit it a bit for upload.
This is a drop-in replacement- same pinion fits, can is the same diameter, holes line up, and original screws match. It actually looks like the 775 that was on there previously had a (red) adapter plate on it:
But the 4274 had no need for it.
Hex sizes needed: 1.5mm, 2.0mm, 2.5mm. Mostly 2.0mm.
To swap the motor, you have to remove the cover to the right of it, which means removing the transmission for this upgrade. Not a ton of work! Remove four 2.0mm screws (two under, two through the chassis rails) that hold it down, the driveshafts, the gear switch spring, and it comes right out.
The cover is held by 3 smaller screws (right to left) 1.5mm, as well as 2 2.0mm screws (left to right). One screw will not clear the motor, remove that one second and the plate comes free. Afterwards 2 2.5mm hex cap screws with washers hold the motor to the plate. You need to remove the pinion to get it out as the pinion does not fit through the plate hole- 2.0mm retaining screw.
The 4274 bolts directly in, no adapters needed, with the smaller hole pattern. It appears there is two orientations you could mount the motor in, one as shown with the cabling facing the camera, then another counter-clockwise 90 degrees, although that will likely interfere with cabling.
The ESC is secured down with hook and loop / velcro. Easy to replace / install. This combo requires soldering, which I am horrific at, but somehow managed this time around. You hook the ESC and Steering Servo up to the light controller board, and the light controller board up to the receiver.
I could not hook up the extra leads on the R3 for dynamic adjustment of the drag brake / etc, as there were no channels left, and I was not yet ready to change the receiver to the FrSky TD, so I skipped hooking those up for now, opting to test the new configuration.
Same pinion same battery, a LOT more pep in its step. Can crawl slow enough you wouldn't notice if you weren't looking hard. Doesn't whine. Unlock the diffs at speed or it will roll. Handles so realistically... its like going from a toy to the real deal. Drives, crawls, and sprints through thick grass without giving a hoot. It isn't "climbing over' the grass as it drives around on the lawn, it simply drives through it like it isn't there.
Simply superb upgrade. I will want to run 4S on this, so I'm hunting for an appropriately sized battery.
Maximum size the battery tray can handle: (LxWxH) 5.5"x2.5"x1.68" / 139x63x42mm.
I've got another R3+4274 on hand for another car thats on its way, as most reviews say the stock power system on it is lethargic.
That I would understand. 
