I know its a waste of time. I know it'd be better off dropping a zetec or CVH in there on carbs and ECS BUT... Has anyone done one?

They're pretty common amongst Minor/MG and Mini owners who bolt them onto their old 1275 engines and fit standard carbs on the end with a richer needle.
That appears to be all you need to do provided you dont run silly bost.
As far as anyone 'official' knows its still a 1300.