I expected the closer distance from rubber to exhaust with the Sunbursts, therefore i asked for the backspace.
That problem is not existing with the real 427 street exhaust routing were the axle loop is partially inside the cutted trunk tub and covered with the always visible covers inside the tub.
In addition to the FIAs I would suggest to mount nothing bigger then 255 at the rear. With my 275 rear, even with deleted resonators and re routed exhaust tube loop the distance on the rh side is quite small. So wrapping with good wrapping tape is necessary.
Next time I need to replace my rear tires (and that will happen soon with the AVONs) I will switch from 275 to 255.