The CL03 series does not share any parts from the Yokomo. The whole car is made of Delrin, graphite, and aluminum. However the front end of the CL03 series can use HPI Pro2 parts. Such as steering hubs and C-hubs.
The Inqubass shares parts with Yokomo(MR4TC). Still a cool design but not to many people race this version.
The new one I bought is the T-4. It also shares front end parts from the Yokomo(Special). Just the steering hubs, steering rack, and C-hubs. The whole layout of this car is nice. I haven't raced it yet but I will know how it is this weekend if it doesn't rain! Some of the parts are Delrin, chassis and top plates are graphite, graphite plastics parts, and the rest is aluminum.
Anyway, I guess OVA's are not popular here in the States.