Without doing much math, I would agree. Your overall 5th gear ratio looks like it would be below 2.50 and that is going to be difficult unless you have a pretty strong engine. A 235 in good nick can and will work with an overall ratio in the mid to higher 2.6 range (mine is 2.65, however I have 15 inch wheels and tires with a bit smaller diameter than yours). On an ideal day without steep hills and wind, I'm just fine. With steep hills and wind I just drop back to 4th and my overall ratio is 3.07.
