I'am to do exactly the same thing with my RC8. But to the place to use the RCM RC8 motor mount, i've use the RCM revo motor mount. Like that, i can leave the center diff on the stock direction. I've put spacer under the center diff mount (you can see it on the pics, it's red Traxxas spacer for the P2 aluminium pushrod), this spacer is need to allow the clutchbell to clear the rear brake calipers. I've use the Tekno elektri clutch adapter with the 26mm flywheel. I've mount the clutch shoes on the leading way to engage sooner.
The clutchbell is Robinson Racing extra hardened 18T (but i can easily mount a 16T. Due to the 4.3 diff ratio on the RC8, this is the only way i've found to can run revo hardened clutchbell. Because on a stadart 3.333 diff ratio, the only 12-14T clutchbell available was not recomand to run against a hardened buggy spur gear.
The only thing i've to do is to mount my brake sevo with Kingheadz servo post.
My motor is a Neu 1515, 1Y/F with an MGM 16018 + flightpower EVO25, 5000mAh, 4s.