Sorry, have you actually seen a Harrison.
Harrison is very similiar to RMC shape, just with some nice little flaring etc. Nothing like a DRB at all.
DRB is definitely a flatter shape. Has the distinctive flat sill at rear of the engine bay. The main advantage of DRB is the wheel profile, all DRB's look like they are dumped into the weeds due to minimal(nill) gap between bottom guards & tyres. The Boss DRB I saw earlier this week had over 100mm clearance even with underbody exhaust and tyres were nicely tucked up into the guards. It looked low. Mind you it helped that it had massive 335's on the rear.
My favourite shape is Robnell, although it's not without it's problems as well. The front guards droop on the Robnell and still suffers from the inconsistancy that most of our bodies here seem to suffer from. eg the rear light mounds are noticeably different heights on Robnell. My favourite feature on Robnell is that nicely flared rear guard, we copied that on our original DRB.
Classic Revival is a very tall body, which you can see in the doors etc. Makes for easy fitment of engines etc.
Most of the manufacturers have changed body shapes over the years.
DRB up to 1995 had smaller rear guard body shape.
Classic Revival changed shapes a while back.
RMC has also changed shape. I actually preferred the earlier RMC shape.
etc etc
I won't go into the sources of the bodies as I don't think that's going to be constructive. Discussing the differences is much more interesting...
From my observations each different body shape has features that are more original than others.
The Superformance looks nothing like any of the other Cobra's here, but I've heard it was scanned from one side of an original car. One side only due to the original bodies not being symetrical.
I would love to have a Kirkham. Some lucky bugger here in Aus has one as the local car broker here in Bris has brought one in.