With the marginal difference in RPMs at highway speeds, I would recommend the 3.73's - even though I have the 3.55's
Pullies are a good mod too. If you're worried about the alternator not getting enough charge from the larger pulley - don't. It really doesn't have that much effect. Unless you are going to be sitting in traffic for hours on end would it really hurt you. I've had my March pulleys on for ~5 years now and have never had a problem - same battery for the last 4 years to boot!
Good luck,
E
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1991 5.0 LX Coupe - 38,000 miles
13.17 @ 106.14 mph w/ 2.138 60'