Maybe it's worth contacting 'Junior Z' (Julien) here on oOple? He has done a carbon chassis for the TRF201 (like the one Lee Martin used at the Cactus Classic,
CLICK) - It's a really flexible chassis and uses a Vega gearbox - I can imagine much the same can be done with an RB6 box though.
The cars I've seen like this always have the stickers 'RED Workshop' on it - and a while back I saw an RB6 with this decal, so who knows they might already have a conversion (which is why I'm mentioning)