Gentlemen,
Many thanks for your response. All very helpful. As suggested I have had a look at the mounting flanges and they may well have been re-faced. I trial fitted the carburettor with some aluminium packing inserted between the flanges and this method will provide the necessary clearance to allow removal of the float chamber bolt. I will make up a correctly shaped/drilled spacer and fit longer studs to do a decent job.
Many thanks/Regards/Ian
