The only reason I can suggest stepping down from 4.10's to 3.73's is that you'll possibly get better times in the 1/4 mile, actually. My car's pretty close to the same as yours - same year, gears, driveshaft, tranny - and I'm at about 5800 RPM when I cross the traps. Getting traction is a major pain, so unless you're running DR's or slicks, you're gonna have to get damned good at your launching technique to make those 4.10's worth it. Your cam and injector setup may change the powerband on yours, but I'd imagine it's likely to make it even worse off in that you'll be redlining before you even cross the traps. Taller/wider rear tires might be an easier/cheaper way to help balance things out than a gear change.
As far as mileage, I average about 22 MPG city/highway mix (mostly highway). The most I've ever seen was one freak occurrance of 26 MPG; the lowest average was about 16 MPG. Switching to 3.73's might gain you 1-2 MPG, tops. I don't have a clue as to how the cam you have will affect your mileage, but I'd imagine it won't be good. I drive about 70 miles a day, myself, so I feel your pain as far as gas cost goes; last month, alone, I spent $210 just in getting to/from work.
At 75 MPH, I'm turning about 2400 RPM - not too high, and actually pretty nice that it keeps it far enough up in the powerband that I can just lay on the gas to get around a slowpoke on the highway, or jam right up a steep incline, without downshifting.
