I don't think that we'll ever see this one as a pre-built. I just bought the kit and it has three metal frets with millions of pieces to build the six rocket cages. It's unbelievable in this scale! I'll have to put this one aside until I have practised on a few, less complex, Dragon 251s which I have in the pipeline. I'll need jeweller's tweezers too ! This kit is a beauty but, unless Dragon make a special effort to make a simpler, plastic construction for the rocket cages, we'll never see it as a pre-built offering.
Which brings me to dboulais' vehicle. Yes, the hybrid model 60140 has come and gone. Strangely, it did not suffer from the same problems as the kit above. Despite having photo-etched metal hull plates which replicated this 251 C's riveted top hull plates which are designed to be located on top of the top plates of the normal 251 C' s body, Dragon wisely included an alternative, entire top hull which has the riveted top plates. This is the top hull assembly which Dragon used for the pre-built issue. I initially thought that the beautifully detailed photo-etched overlay plates were used in this pre-built, but I now recognise, and am now convinced that, Dragon must use plastic where this is available. The time and skill needed to use the photo-etched parts must be very costly. Still, the shell-case frames at the rear fighting compartments of those 251s which have 37mm AT guns are metal, photo-etched parts, I believe.
So, the short answer to the question is that model number 60140 has come and gone.
Some'll turn up, I'm sure.
MoMo