I have an FF-03R, but it's a shelf-queen. The 36/77 gearing is on my rear-motor XV-01 road car. I didn't modify the motor mount. The XV-01 motor mount has a minimum tooth count (add the pinion and spur teeth together) of 100 @ 48-pitch and a maximum tooth count of about ~115 @ 48-pitch, though I've only tested fitment up to 113.
My rear-motor XV-01 is essentially a XV-01TC with a widened track-width and the motor in the back, so yes, it can be done. I used the front A-arms from the FF-03 and the rear A-arms from the TA-06. The real XV-01TC uses the front *and* rear A-arms from the FF-03. (they're actually used on several vehicles designed around the same timeframe, but the FF-03 is the one that comes to mind.) The only snag is that the XV-01TC needs slightly longer shock shafts to achieve the same ride-height front and rear, or else you have to travel-limit the rear shocks and lower the car. If you have smooth pavement to drive on that's not a problem, but forget about running it as a rally car ever again.
Increasing wheel offset by getting wider hexes only works if there's enough exposed stub-axle length to allow you to securely tighten the wheel nuts. There are thin locknuts that rely on the serrations alone to secure them, and have no nylon insert, so they need less exposed stub-axle length than normal wheel nuts; Tamiya sells blue aluminum ones and Vaterra sells black steel ones. I kept the stock hexes and instead used wider-offset wheels on my rear-motor XV-01, in combination with wider toe-blocks. There aren't any options for wider toe-blocks if you keep the stock rally-style suspension, though.
Softer springs will still feel really stiff over bumps if the damper oil is still thick -- in fact, they might pack-down over multiple bumps, as the softer springs won't be able to re-extend the shocks fast enough. Something someone explained to me when I was fighting with the suspension on my Yeti: Drain the shocks, and bounce-test the car with different springs until it bounces evenly front-and-rear, or as close as you can get. Only then refill the shocks and test different oil weights until you get bottoming-out and rebound-bouncing under control.
If your tires are badly coned, then it sounds like you need to dial-in more negative camber so the tires wear more evenly. I'm not a believer in adjusting the camber for maximum grip, I think that's the job of the shocks, swaybars, roll-center adjustments, and tire compound. Camber should be adjusted to achieve even tire-wear based on your driving style.
http://www.rctech.net/forum/electric...a-rr-01-a.html
I don't know any other XV-01 drivers. I just made up answers to my questions.