Besides the bellhousing and the fork (the v8 one is the same fork but has no weights on it) The V8 T5 has longer and less optimal go fast ratios but the long first gear is supposed to be a bit stronger just because of the ratio on the thing. I think in a VN or VP or anything else lightish it would be just fine though. In the states and England race cars are runing T5's with straight cut gears that are rated for over 600hp, expensive but good since you still have yourself a 40kg box
. The input shaft is an inch longer on the V6 than the V8, you can either make an adapter or cut the shaft. Both box's apart from the ratios are the same and are both the "world class" style T5