There's a few reasons that are driving me to changing:
-The Clio box suits the road, nice and snappy through the gears, but on a track and especially with a pit of power 145mph on the limiter with a meg engine its just not quick enough.
-The bell housing isn't deep enough for the meg clutch so you are restricted to run a uprated clio item.
-The clio box really needs a diff with anything over 250lb to make good use of it, where as the later meg ones have one as standard.