BMI make conversions for the Xray T2, HB Cyclone, TC3/4, but they are mostly just tweaked original chassis.
Diggety Designs do a nice TC4 chassis, but its expensive.
I have loads of ideas for a custom TC chassis, mainly along the lines of a 2 deck, single belt JRXS, or an improved RC Lab, but a. I haven't got the time and b. I haven't got the money.
Anyone want to fund me?