To improve it? How about replacing the american engine with one from Japan or even the MotoGuzzi V twin?
How would that improve it, Howard? S&S engines are robust enough, plenty of character & torque, eminently tuneable and rare enough this side of the pond.
After two years of production, the car now has it's own identity firmly etched in time.
I would go along with a specific 'hot' engine model, but to start at the very beginning and homologate the engine is financial suicide given the sales it would attract. Add to this, a new driveline would be needed & it's never going to be a runner.
Who's going to be first to cam up their S&S I wonder..?