Woz..It's a trick of the light. Early thin fin barrel, single piece rockerbox, dynamo end of the timing cover pointing slightly upwards (Longstroke is flat). It is an early A10 type.
Between the carb looks to be some kind of adaptor tract, directing the inlet to the left hand side of the frame tube. More style than function, but that's part of the charm of this sort of build.
The bad news is that Owen's Alloy head won't match the thin fin barrel. It will fit as regards the holes, but will overhang the barrel, and as musko says, space around the carb may be a problem.
Owen, Hi, Welcome, Nice Pipes!
Swarfy.