Fired it up again last night, I'm really happy with how it runs on such a basic tune-up. Tick-over nice at about 800 rpm, a little lumpy in places, but I've yet to fine tune the ignition timing and the carbs will need setting up again for this engine.
Couple of minor issues:
Water leaks - at the back of the water pump (pipe that runs behind the manifold) and the bottom hose.
Exhaust blowing - my Frankenstein's monster bitsa exhaust system needs taking off, joints cleaning and properly reassembling instead of just shoving it on and hoping for the best.
Something to do this weekend!