2.76 to 3.91's SG

The rear end is out of the car so I can move it accordingly. I'd like to cruise around in it quite a bit. Not just city driving. My current 7 1/4 has 2.94 gears and was a dog sometimes going up hills. Is it really that unbearable. Besides gas mileage, I'd assume the exhaust could get annoying at the higher rpms. I have a stock exhaust with some aftermarket muffler. I just don't know if I should make the buy since I have no idea when my car is going to run again.