It's really the nose to nose playing surface that matters, a ball can only be against the cushion...not beyond. An 8 footer is 44 x 88 and the oversized 8 is 46 x 92. So if you have an inch to spare on the sides and 2 inches to spare at the ends on shots today you are good to go.
I don't totally disagree with looking at the overall size because wider rails will allow your bridge to be further beyond the cushion nose and potentially lead to a longer backstroke that requires more wall clearance than a narrow rail but those situations are rare and the playing field is the primary starting point. And don't just add the cue length, allow for 6 inches of you can for backstroke. If you crunch the numbers, the gold crown rails are about 1.5 inches wider per side than your current table and as noted above the playing field is 1-2 inches per side bigger. So I suppose worst case you need an extra 2.5 and 3.5 inches on the sides and ends respectively.