Thanks for your suggestions one and all. I sat in the garage last night and carefully unfolded the much abused thin metal tag on the float chamber on one of the carbs, CAREFULLY unfolding this fragile bit of tin. Slowly and softly brushing the 50 years of tarnish off. The number, albeit hardley readable, slowly began to appear.. Let's see, ahhh 'A', then, yes I think, 'UC' then ahh 8....6....6... the tag then gave up the ghost to become several bits of tin... Soooo, AUC 866... correct carb!!! Then I realized that whoever put these carbs back together, assembled the butterflies and all associated linkages -- well let's say incorrectly. Although faced with a rear float chamber on the front carb... We are in business...
By the way the AUC 6040 number on the housing was exactly that, the housing number.. not the carb number... This is why we love the British and their cars so much!!!
Happy LBC'ing... Ron