i have a standard 1979 austin mini with standard drums standard arches, when going 4/5 up or a heavy load my tyres/wheel scrape and make a nice squeak

basically i want to get new wheels that are 6x10 black mambas, obviously this will make the rubbing even worse and probs wont even be able to turn the wheel!! its rubbing on the main frame of the body not the wheel arches, to get these what will i have to do to stop all rubbing etc, i want to know size of spaces needed, the size of the wheel arches (group 2 perhaps?) and then a decent tyre that wont look overly stupid! i want to go wide but not some fatboy mini just generally give it some shape, cheers guys! :)