Starting with the ups. I managed to sort out the exhaust. One of the joints had to be sleeved to make a gas tight seal and with the help of my neighbour I got it done. While the exhaust itself isn't blowing there is a blow where the manifold is bolted on to the cylinder head. I've fitted the carbs and it has improved performance.
Moving on to the downs. As soon as I'd got Brown running after the carb swap a squealing noise has appeared which only disappears when I'm accelerating under load. This has marred an otherwise great day of achievements.