Good stuff Bill.
The Harvard, as supplied to RAF and Commonwealth air forces, had the 'fighter style' stick grip, as you've discovered, and there were a few other fittings that were 'British', for want of a better term. Some of these depended on the factory, and the model type ( I believe their were more differences on Canadian-produced aircraft), and the rear (fixed) canopy,sometimes longer, depending on model, seat harnesses, some instruments, undercarriage doors (or lack of), and the type of exhaust are examples.
The exhaust, in particular, often quickly identified a Harvard, as opposed to Texan, AT6 etc, from certain angles, and this was normally the extended type, as seen in the two photos I posted, and on the model of the Boscombe Down aircraft I built.
Of course, having access to the actual aircraft being modelled should be an enormous advantage.